Archive for the 'general equilibrium' Category

Phillips Curve Musings: Addendum on Budget Deficits and Interest Rates

In my previous post, I discussed a whole bunch of stuff, but I spent a lot of time discussing the inappropriate use of partial-equilibrium supply-demand analysis to explain price and quantity movements when price and quantity movements in those markets are dominated by precisely those forces that are supposed to be held constant — the old ceteris paribus qualification — in doing partial equilibrium analysis. Thus, the idea that in a depression or deep recession, high unemployment can be cured by cutting nominal wages is a classic misapplication of partial equilibrium analysis in a situation in which the forces primarily affecting wages and employment are not confined to a supposed “labor market,” but reflect broader macro-economic conditions. As Keynes understood, but did not explain well to his economist readers, analyzing unemployment in terms of the wage rate is futile, because wage changes induce further macroeconomic effects that may counteract whatever effects resulted from the wage changes.

Well, driving home this afternoon, I was listening to Marketplace on NPR with Kai Ryssdal interviewing Neil Irwin. Ryssdal asked Irwin why there is so much nervousness about the economy when unemployment and inflation are both about as low as they have ever been — certainly at the same time — in the last 50 years. Irwin’s response was that it is unsettling to many people that, with budget deficits high and rising, we observe stable inflation and falling interest rates on long-term Treasuries. This, after we have been told for so long that budget deficits drive up the cost of borrowing money and also cause are a major cause of inflation. The cognitive dissonance of stable inflation, falling interest rates and rapidly rising budget deficits, Irwin suggested, accounts for a vague feeling of disorientation, and gives rise to fears that the current apparent stability can’t last very long and will lead to some sort of distress or crisis in the future.

I’m not going to try to reassure Ryssdal and Irwin that there will never be another crisis. I certainly wouldn’t venture to say that all is now well with the Republic, much less with the rest of the world. I will just stick to the narrow observation that the bad habit of predicting the future course of interest rates by the size of the current budget deficit has no basis in economic theory, and reflects a colossal misunderstanding of how interest rates are determined. And that misunderstanding is precisely the one I discussed in my previous post about the misuse of partial-equilibrium analysis when general-equilibrium analysis is required.

To infer anything about interest rates from the market for government debt is a category error. Government debt is a long-lived financial asset providing an income stream, and its price reflects the current value of the promised income stream. Based on the price of a particular instrument with a given duration, it is possible to calculate a corresponding interest rate. That calculation is just a fairly simple mathematical exercise.

But it is a mistake to think that the interest rate for that duration is determined in the market for government debt of that duration. Why? Because, there are many other physical assets or financial instruments that could be held instead of government debt of any particular duration. And asset holders in a financially sophisticated economy can easily shift from one type of asset to another at will, at fairly minimal transactions costs. So it is very unlikely that any long-lived asset is so special that the expected yield from holding that asset varies independently from the expected yield from holding alternative assets that could be held.

That’s not to say that there are no differences in the expected yields from different assets, just that at the margin, taking into account the different characteristics of different assets, their expected returns must be fairly closely connected, so that any large change in the conditions in the market for any single asset are unlikely to have a large effect on the price of that asset alone. Rather, any change in one market will cause shifts in asset-holdings across different markets that will tend to offset the immediate effect that would have been reflected in a single market viewed in isolation.

This holds true as long as each specific market is relatively small compared to the entire economy. That is certainly true for the US economy and the world economy into which the US economy is very closely integrated. The value of all assets — real and financial — dwarfs the total outstanding value of US Treasuries. Interest rates are a measure of the relationship between expected flows of income and the value of the underlying assets.

To assume that increased borrowing by the US government to fund a substantial increase in the US budget deficit will substantially affect the overall economy-wide relationship between current and expected future income flows on the one hand and asset values on the other is wildly implausible. So no one should be surprised to find that the recent sharp increase in the US budget deficit has had no perceptible effect on the interest rates at which US government debt is now yielding.

A more likely cause of a change in interest rates would be an increase in expected inflation, but inflation expectations are not necessarily correlated with the budget deficit, and changing inflation expectations aren’t necessarily reflected in corresponding changes in nominal interest rates, as Monetarist economists have often maintained.

So it’s about time that we disabused ourselves of the simplistic notion that changes in the budget deficit have any substantial effect on interest rates.

Phillips Curve Musings

There’s a lot of talk about the Phillips Curve these days; people wonder why, with the unemployment rate reaching historically low levels, nominal and real wages have increased minimally with inflation remaining securely between 1.5 and 2%. The Phillips Curve, for those untutored in basic macroeconomics, depicts a relationship between inflation and unemployment. The original empirical Philips Curve relationship showed that high rates of unemployment were associated with low or negative rates of wage inflation while low rates of unemployment were associated with high rates of wage inflation. This empirical relationship suggested a causal theory that the rate of wage increase tends to rise when unemployment is low and tends to fall when unemployment is high, a causal theory that seems to follow from a simple supply-demand model in which wages rise when there is an excess demand for labor (unemployment is low) and wages fall when there is an excess supply of labor (unemployment is high).

Viewed in this light, low unemployment, signifying a tight labor market, signals that inflation is likely to rise, providing a rationale for monetary policy to be tightened to prevent inflation from rising at it normally does when unemployment is low. Seeming to accept that rationale, the Fed has gradually raised interest rates for the past two years or so. But the increase in interest rates has now slowed the expansion of employment and decline in unemployment to historic lows. Nor has the improving employment situation resulted in any increase in price inflation and at most a minimal increase in the rate of increase in wages.

In a couple of previous posts about sticky wages (here and here), I’ve questioned whether the simple supply-demand model of the labor market motivating the standard interpretation of the Phillips Curve is a useful way to think about wage adjustment and inflation-employment dynamics. I’ve offered a few reasons why the supply-demand model, though applicable in some situations, is not useful for understanding how wages adjust.

The particular reason that I want to focus on here is Keynes’s argument in chapter 19 of the General Theory (though I express it in terms different from his) that supply-demand analysis can’t explain how wages and employment are determined. The upshot of his argument I believe is that supply demand-analysis only works in a partial-equilibrium setting in which feedback effects from the price changes in the market under consideration don’t affect equilibrium prices in other markets, so that the position of the supply and demand curves in the market of interest can be assumed stable even as price and quantity in that market adjust from one equilibrium to another (the comparative-statics method).

Because the labor market, affecting almost every other market, is not a small part of the economy, partial-equilibrium analysis is unsuitable for understanding that market, the normal stability assumption being untenable if we attempt to trace the adjustment from one labor-market equilibrium to another after an exogenous disturbance. In the supply-demand paradigm, unemployment is a measure of the disequilibrium in the labor market, a disequilibrium that could – at least in principle — be eliminated by a wage reduction sufficient to equate the quantity of labor services supplied with the amount demanded. Viewed from this supply-demand perspective, the failure of the wage to fall to a supposed equilibrium level is attributable to some sort of endogenous stickiness or some external impediment (minimum wage legislation or union intransigence) in wage adjustment that prevents the normal equilibrating free-market adjustment mechanism. But the habitual resort to supply-demand analysis by economists, reinforced and rewarded by years of training and professionalization, is actually misleading when applied in an inappropriate context.

So Keynes was right to challenge this view of a potentially equilibrating market mechanism that is somehow stymied from behaving in the manner described in the textbook version of supply-demand analysis. Instead, Keynes argued that the level of employment is determined by the level of spending and income at an exogenously given wage level, an approach that seems to be deeply at odds with idea that price adjustments are an essential part of the process whereby a complex economic system arrives at, or at least tends to move toward, an equilibrium.

One of the main motivations for a search for microfoundations in the decades after the General Theory was published was to be able to articulate a convincing microeconomic rationale for persistent unemployment that was not eliminated by the usual tendency of market prices to adjust to eliminate excess supplies of any commodity or service. But Keynes was right to question whether there is any automatic market mechanism that adjusts nominal or real wages in a manner even remotely analogous to the adjustment of prices in organized commodity or stock exchanges – the sort of markets that serve as exemplars of automatic price adjustments in response to excess demands or supplies.

Keynes was also correct to argue that, even if there was a mechanism causing automatic wage adjustments in response to unemployment, the labor market, accounting for roughly 60 percent of total income, is so large that any change in wages necessarily affects all other markets, causing system-wide repercussions that might well offset any employment-increasing tendency of the prior wage adjustment.

But what I want to suggest in this post is that Keynes’s criticism of the supply-demand paradigm is relevant to any general-equilibrium system in the following sense: if a general-equilibrium system is considered from an initial non-equilibrium position, does the system have any tendency to move toward equilibrium? And to make the analysis relatively tractable, assume that the system is such that a unique equilibrium exists. Before proceeding, I also want to note that I am not arguing that traditional supply-demand analysis is necessarily flawed; I am just emphasizing that traditional supply-demand analysis is predicated on a macroeconomic foundation: that all markets but the one under consideration are in, or are in the neighborhood of, equilibrium. It is only because the system as a whole is in the neighborhood of equilibrium, that the microeconomic forces on which traditional supply-demand analysis relies appear to be so powerful and so stabilizing.

However, if our focus is a general-equilibrium system, microeconomic supply-demand analysis of a single market in isolation provides no basis on which to argue that the system as a whole has a self-correcting tendency toward equilibrium. To make such an argument is to commit a fallacy of composition. The tendency of any single market toward equilibrium is premised on an assumption that all markets but the one under analysis are already at, or in the neighborhood of, equilibrium. But when the system as a whole is in a disequilibrium state, the method of partial equilibrium analysis is misplaced; partial-equilibrium analysis provides no ground – no micro-foundation — for an argument that the adjustment of market prices in response to excess demands and excess supplies will ever – much less rapidly — guide the entire system back to an equilibrium state.

The lack of automatic market forces that return a system not in the neighborhood — for purposes of this discussion “neighborhood” is left undefined – of equilibrium back to equilibrium is implied by the Sonnenschein-Mantel-Debreu Theorem, which shows that, even if a unique general equilibrium exists, there may be no rule or algorithm for increasing (decreasing) prices in markets with excess demands (supplies) by which the general-equilibrium price vector would be discovered in a finite number of steps.

The theorem holds even under a Walrasian tatonnement mechanism in which no trading at disequilibrium prices is allowed. The reason is that the interactions between individual markets may be so complicated that a price-adjustment rule will not eliminate all excess demands, because even if a price adjustment reduces excess demand in one market, that price adjustment may cause offsetting disturbances in one or more other markets. So, unless the equilibrium price vector is somehow hit upon by accident, no rule or algorithm for price adjustment based on the excess demand in each market will necessarily lead to discovery of the equilibrium price vector.

The Sonnenschein Mantel Debreu Theorem reinforces the insight of Kenneth Arrow in an important 1959 paper “Toward a Theory of Price Adjustment,” which posed the question: how does the theory of perfect competition account for the determination of the equilibrium price at which all agents can buy or sell as much as they want to at the equilibrium (“market-clearing”) price? As Arrow observed, “there exists a logical gap in the usual formulations of the theory of perfectly competitive economy, namely, that there is no place for a rational decision with respect to prices as there is with respect to quantities.”

Prices in perfect competition are taken as parameters by all agents in the model, and optimization by agents consists in choosing optimal quantities. The equilibrium solution allows the mutually consistent optimization by all agents at the equilibrium price vector. This is true for the general-equilibrium system as a whole, and for partial equilibrium in every market. Not only is there no positive theory of price adjustment within the competitive general-equilibrium model, as pointed out by Arrow, but the Sonnenschein-Mantel-Debreu Theorem shows that there’s no guarantee that even the notional tatonnement method of price adjustment can ensure that a unique equilibrium price vector will be discovered.

While acknowledging his inability to fill the gap, Arrow suggested that, because perfect competition and price taking are properties of general equilibrium, there are inevitably pockets of market power, in non-equilibrium states, so that some transactors in non-equilibrium states, are price searchers rather than price takers who therefore choose both an optimal quantity and an optimal price. I have no problem with Arrow’s insight as far as it goes, but it still doesn’t really solve his problem, because he couldn’t explain, even intuitively, how a disequilibrium system with some agents possessing market power (either as sellers or buyers) transitions into an equilibrium system in which all agents are price-takers who can execute their planned optimal purchases and sales at the parametric prices.

One of the few helpful, but, as far as I can tell, totally overlooked, contributions of the rational-expectations revolution was to solve (in a very narrow sense) the problem that Arrow identified and puzzled over, although Hayek, Lindahl and Myrdal, in their original independent formulations of the concept of intertemporal equilibrium, had already provided the key to the solution. Hayek, Lindahl, and Myrdal showed that an intertemporal equilibrium is possible only insofar as agents form expectations of future prices that are so similar to each other that, if future prices turn out as expected, the agents would be able to execute their planned sales and purchases as expected.

But if agents have different expectations about the future price(s) of some commodity(ies), and if their plans for future purchases and sales are conditioned on those expectations, then when the expectations of at least some agents are inevitably disappointed, those agents will necessarily have to abandon (or revise) the plans that their previously formulated plans.

What led to Arrow’s confusion about how equilibrium prices are arrived at was the habit of thinking that market prices are determined by way of a Walrasian tatonnement process (supposedly mimicking the haggling over price by traders). So the notion that a mythical market auctioneer, who first calls out prices at random (prix cries au hasard), and then, based on the tallied market excess demands and supplies, adjusts those prices until all markets “clear,” is untenable, because continual trading at disequilibrium prices keeps changing the solution of the general-equilibrium system. An actual system with trading at non-equilibrium prices may therefore be moving away from, rather converging on, an equilibrium state.

Here is where the rational-expectations hypothesis comes in. The rational-expectations assumption posits that revisions of previously formulated plans are never necessary, because all agents actually do correctly anticipate the equilibrium price vector in advance. That is indeed a remarkable assumption to make; it is an assumption that all agents in the model have the capacity to anticipate, insofar as their future plans to buy and sell require them to anticipate, the equilibrium prices that will prevail for the products and services that they plan to purchase or sell. Of course, in a general-equilibrium system, all prices being determined simultaneously, the equilibrium prices for some future prices cannot generally be forecast in isolation from the equilibrium prices for all other products. So, in effect, the rational-expectations hypothesis supposes that each agent in the model is an omniscient central planner able to solve an entire general-equilibrium system for all future prices!

But let us not be overly nitpicky about details. So forget about false trading, and forget about the Sonnenschein-Mantel-Debreu theorem. Instead, just assume that, at time t, agents form rational expectations of the future equilibrium price vector in period (t+1). If agents at time t form rational expectations of the equilibrium price vector in period (t+1), then they may well assume that the equilibrium price vector in period t is equal to the expected price vector in period (t+1).

Now, the expected price vector in period (t+1) may or may not be an equilibrium price vector in period t. If it is an equilibrium price vector in period t as well as in period (t+1), then all is right with the world, and everyone will succeed in buying and selling as much of each commodity as he or she desires. If not, prices may or may not adjust in response to that disequilibrium, and expectations may or may not change accordingly.

Thus, instead of positing a mythical auctioneer in a contrived tatonnement process as the mechanism whereby prices are determined for currently executed transactions, the rational-expectations hypothesis posits expected future prices as the basis for the prices at which current transactions are executed, providing a straightforward solution to Arrow’s problem. The prices at which agents are willing to purchase or sell correspond to their expectations of prices in the future. If they find trading partners with similar expectations of future prices, they will reach agreement and execute transactions at those prices. If they don’t find traders with similar expectations, they will either be unable to transact, or will revise their price expectations, or they will assume that current market conditions are abnormal and then decide whether to transact at prices different from those they had expected.

When current prices are more favorable than expected, agents will want to buy or sell more than they would have if current prices were equal to their expectations for the future. If current prices are less favorable than they expect future prices to be, they will not transact at all or will seek to buy or sell less than they would have bought or sold if current prices had equaled expected future prices. The dichotomy between observed current prices, dictated by current demands and supplies, and expected future prices is unrealistic; all current transactions are made with an eye to expected future prices and to their opportunities to postpone current transactions until the future, or to advance future transactions into the present.

If current prices for similar commodities are not uniform in all current transactions, a circumstance that Arrow attributes to the existence of varying degrees of market power across imperfectly competitive suppliers, price dispersion may actually be caused, not by market power, but by dispersion in the expectations of future prices held by agents. Sellers expecting future prices to rise will be less willing to sell at relatively low prices now than are suppliers with pessimistic expectations about future prices. Equilibrium occurs when all transactors share the same expectations of future prices and expected future prices correspond to equilibrium prices in the current period.

Of course, that isn’t the only possible equilibrium situation. There may be situations in which a future event that will change a subset of prices can be anticipated. If the anticipation of the future event affects not only expected future prices, it must also and necessarily affect current prices insofar as current supplies can be carried into the future from the present or current purchases can be postponed until the future or future consumption shifted into the present.

The practical upshot of these somewhat disjointed reflections is, I think,primarily to reinforce skepticism that the traditional Phillips Curve supposition that low and falling unemployment necessarily presages an increase in inflation. Wages are not primarily governed by the current state of the labor market, whatever the labor market might even mean in macroeconomic context.

Expectations rule! And the rational-expectations revolution to the contrary notwithstanding, we have no good theory of how expectations are actually formed and there is certainly no reason to assume that, as a general matter, all agents share the same set of expectations.

The current fairly benign state of the economy reflects the absence of any serious disappointment of price expectations. If an economy is operating not very far from an equilibrium, although expectations are not the same, they likely are not very different. They will only be very different after the unexpected strikes. When that happens, borrowers and traders who had taken positions based on overly optimistic expectations find themselves unable to meet their obligations. It is only then that we will see whether the economy is really as strong and resilient as it now seems.

Expecting the unexpected is hard to do, but you can be sure that, sooner or later, the unexpected is going to happen.

More on Sticky Wages

It’s been over four and a half years since I wrote my second most popular post on this blog (“Why are Wages Sticky?”). Although the post was linked to and discussed by Paul Krugman (which is almost always a guarantee of getting a lot of traffic) and by other econoblogosphere standbys like Mark Thoma and Barry Ritholz, unlike most of my other popular posts, it has continued ever since to attract a steady stream of readers. It’s the posts that keep attracting readers long after their original expiration date that I am generally most proud of.

I made a few preliminary points about wage stickiness before getting to my point. First, although Keynes is often supposed to have used sticky wages as the basis for his claim that market forces, unaided by stimulus to aggregate demand, cannot automatically eliminate cyclical unemployment within the short or even medium term, he actually devoted a lot of effort and space in the General Theory to arguing that nominal wage reductions would not increase employment, and to criticizing economists who blamed unemployment on nominal wages fixed by collective bargaining at levels too high to allow all workers to be employed. So, the idea that wage stickiness is a Keynesian explanation for unemployment doesn’t seem to me to be historically accurate.

I also discussed the search theories of unemployment that in some ways have improved our understanding of why some level of unemployment is a normal phenomenon even when people are able to find jobs fairly easily and why search and unemployment can actually be productive, enabling workers and employers to improve the matches between the skills and aptitudes that workers have and the skills and aptitudes that employers are looking for. But search theories also have trouble accounting for some basic facts about unemployment.

First, a lot of job search takes place when workers have jobs while search theories assume that workers can’t or don’t search while they are employed. Second, when unemployment rises in recessions, it’s not because workers mistakenly expect more favorable wage offers than employers are offering and mistakenly turn down job offers that they later regret not having accepted, which is a very skewed way of interpreting what happens in recessions; it’s because workers are laid off by employers who are cutting back output and idling production lines.

I then suggested the following alternative explanation for wage stickiness:

Consider the incentive to cut price of a firm that can’t sell as much as it wants [to sell] at the current price. The firm is off its supply curve. The firm is a price taker in the sense that, if it charges a higher price than its competitors, it won’t sell anything, losing all its sales to competitors. Would the firm have any incentive to cut its price? Presumably, yes. But let’s think about that incentive. Suppose the firm has a maximum output capacity of one unit, and can produce either zero or one units in any time period. Suppose that demand has gone down, so that the firm is not sure if it will be able to sell the unit of output that it produces (assume also that the firm only produces if it has an order in hand). Would such a firm have an incentive to cut price? Only if it felt that, by doing so, it would increase the probability of getting an order sufficiently to compensate for the reduced profit margin at the lower price. Of course, the firm does not want to set a price higher than its competitors, so it will set a price no higher than the price that it expects its competitors to set.

Now consider a different sort of firm, a firm that can easily expand its output. Faced with the prospect of losing its current sales, this type of firm, unlike the first type, could offer to sell an increased amount at a reduced price. How could it sell an increased amount when demand is falling? By undercutting its competitors. A firm willing to cut its price could, by taking share away from its competitors, actually expand its output despite overall falling demand. That is the essence of competitive rivalry. Obviously, not every firm could succeed in such a strategy, but some firms, presumably those with a cost advantage, or a willingness to accept a reduced profit margin, could expand, thereby forcing marginal firms out of the market.

Workers seem to me to have the characteristics of type-one firms, while most actual businesses seem to resemble type-two firms. So what I am suggesting is that the inability of workers to take over the jobs of co-workers (the analog of output expansion by a firm) when faced with the prospect of a layoff means that a powerful incentive operating in non-labor markets for price cutting in response to reduced demand is not present in labor markets. A firm faced with the prospect of being terminated by a customer whose demand for the firm’s product has fallen may offer significant concessions to retain the customer’s business, especially if it can, in the process, gain an increased share of the customer’s business. A worker facing the prospect of a layoff cannot offer his employer a similar deal. And requiring a workforce of many workers, the employer cannot generally avoid the morale-damaging effects of a wage cut on his workforce by replacing current workers with another set of workers at a lower wage than the old workers were getting.

I think that what I wrote four years ago is clearly right, identifying an important reason for wage stickiness. But there’s also another reason that I didn’t mention then, but whose importance has since come to appear increasingly significant to me, especially as a result of writing and rewriting my paper “Hayek, Hicks, Radner and three concepts of intertemporal equilibrium.”

If you are unemployed because the demand for your employer’s product has gone down, and your employer, planning to reduce output, is laying off workers no longer needed, how could you, as an individual worker, unconstrained by a union collective-bargaining agreement or by a minimum-wage law, persuade your employer not to lay you off? Could you really keep your job by offering to accept a wage cut — no matter how big? If you are being laid off because your employer is reducing output, would your offer to work at a lower wage cause your employer to keep output unchanged, despite a reduction in demand? If not, how would your offer to take a pay cut help you keep your job? Unless enough workers are willing to accept a big enough wage cut for your employer to find it profitable to maintain current output instead of cutting output, how would your own willingness to accept a wage cut enable you to keep your job?

Now, if all workers were to accept a sufficiently large wage cut, it might make sense for an employer not to carry out a planned reduction in output, but the offer by any single worker to accept a wage cut certainly would not cause the employer to change its output plans. So, if you are making an independent decision whether to offer to accept a wage cut, and other workers are making their own independent decisions about whether to accept a wage cut, would it be rational for you or any of them to accept a wage cut? Whether it would or wouldn’t might depend on what each worker was expecting other workers to do. But certainly given the expectation that other workers are not offering to accept a wage cut, why would it make any sense for any worker to be the one to offer to accept a wage cut? Would offering to accept a wage cut, increase the likelihood that a worker would be one of the lucky ones chosen not to be laid off? Why would offering to accept a wage cut that no one else was offering to accept, make the worker willing to work for less appear more desirable to the employer than the others that wouldn’t accept a wage cut? One reaction by the employer might be: what’s this guy’s problem?

Combining this way of looking at the incentives workers have to offer to accept wage reductions to keep their jobs with my argument in my post of four years ago, I now am inclined to suggest that unemployment as such provides very little incentive for workers and employers to cut wages. Price cutting in periods of excess supply is often driven by aggressive price cutting by suppliers with large unsold inventories. There may be lots of unemployment, but no one is holding a large stock of unemployed workers, and no is in a position to offer low wages to undercut the position of those currently employed at  nominal wages that, arguably, are too high.

That’s not how labor markets operate. Labor markets involve matching individual workers and individual employers more or less one at a time. If nominal wages fall, it’s not because of an overhang of unsold labor flooding the market; it’s because something is changing the expectations of workers and employers about what wage will be offered by employers, and accepted by workers, for a particular kind of work. If the expected wage is too high, not all workers willing to work at that wage will find employment; if it’s too low, employers will not be able to find as many workers as they would like to hire, but the situation will not change until wage expectations change. And the reason that wage expectations change is not because the excess demand for workers causes any immediate pressure for nominal wages to rise.

The further point I would make is that the optimal responses of workers and the optimal responses of their employers to a recessionary reduction in demand, in which the employers, given current input and output prices, are planning to cut output and lay off workers, are mutually interdependent. While it is, I suppose, theoretically possible that if enough workers decided to immediately offer to accept sufficiently large wage cuts, some employers might forego plans to lay off their workers, there are no obvious market signals that would lead to such a response, because such a response would be contingent on a level of coordination between workers and employers and a convergence of expectations about future outcomes that is almost unimaginable.

One can’t simply assume that it is in the independent self-interest of every worker to accept a wage cut as soon as an employer perceives a reduced demand for its product, making the current level of output unprofitable. But unless all, or enough, workers decide to accept a wage cut, the optimal response of the employer is still likely to be to cut output and lay off workers. There is no automatic mechanism by which the market adjusts to demand shocks to achieve the set of mutually consistent optimal decisions that characterizes a full-employment market-clearing equilibrium. Market-clearing equilibrium requires not merely isolated price and wage cuts by individual suppliers of inputs and final outputs, but a convergence of expectations about the prices of inputs and outputs that will be consistent with market clearing. And there is no market mechanism that achieves that convergence of expectations.

So, this brings me back to Keynes and the idea of sticky wages as the key to explaining cyclical fluctuations in output and employment. Keynes writes at the beginning of chapter 19 of the General Theory.


A reduction in money-wages is quite capable in certain circumstances of affording a stimulus to output, as the classical theory supposes. My difference from this theory is primarily a difference of analysis. . . .

The generally accept explanation is . . . quite a simple one. It does not depend on roundabout repercussions, such as we shall discuss below. The argument simply is that a reduction in money wages will, cet. par. Stimulate demand by diminishing the price of the finished product, and will therefore increase output, and will therefore increase output and employment up to the point where  the reduction which labour has agreed to accept in its money wages is just offset by the diminishing marginal efficiency of labour as output . . . is increased. . . .

It is from this type of analysis that I fundamentally differ.

[T]his way of thinking is probably reached as follows. In any given industry we have a demand schedule for the product relating the quantities which can be sold to the prices asked; we have a series of supply schedules relating the prices which will be asked for the sale of different quantities. .  . and these schedules between them lead up to a further schedule which, on the assumption that other costs are unchanged . . . gives us the demand schedule for labour in the industry relating the quantity of employment to different levels of wages . . . This conception is then transferred . . . to industry as a whole; and it is supposed, by a parity of reasoning, that we have a demand schedule for labour in industry as a whole relating the quantity of employment to different levels of wages. It is held that it makes no material difference to this argument whether it is in terms of money-wages or of real wages. If we are thinking of real wages, we must, of course, correct for changes in the value of money; but this leaves the general tendency of the argument unchanged, since prices certainly do not change in exact proportion to changes in money wages.

If this is the groundwork of the argument . . ., surely it is fallacious. For the demand schedules for particular industries can only be constructed on some fixed assumption as to the nature of the demand and supply schedules of other industries and as to the amount of aggregate effective demand. It is invalid, therefore, to transfer the argument to industry as a whole unless we also transfer our assumption that the aggregate effective demand is fixed. Yet this assumption amount to an ignoratio elenchi. For whilst no one would wish to deny the proposition that a reduction in money-wages accompanied by the same aggregate demand as before will be associated with an increase in employment, the precise question at issue is whether the reduction in money wages will or will not be accompanied by the same aggregate effective demand as before measured in money, or, at any rate, measured by an aggregate effective demand which is not reduced in full proportion to the reduction in money-wages. . . But if the classical theory is not allowed to extend by analogy its conclusions in respect of a particular industry to industry as a whole, it is wholly unable to answer the question what effect on employment a reduction in money-wages will have. For it has no method of analysis wherewith to tackle the problem. (General Theory, pp. 257-60)

Keynes’s criticism here is entirely correct. But I would restate slightly differently. Standard microeconomic reasoning about preferences, demand, cost and supply is partial-equilbriium analysis. The focus is on how equilibrium in a single market is achieved by the adjustment of the price in a single market to equate the amount demanded in that market with amount supplied in that market.

Supply and demand is a wonderful analytical tool that can illuminate and clarify many economic problems, providing the key to important empirical insights and knowledge. But supply-demand analysis explicitly – but too often without realizing its limiting implications – assumes that other prices and incomes in other markets are held constant. That assumption essentially means that the market – i.e., the demand, cost and supply curves used to represent the behavioral characteristics of the market being analyzed – is small relative to the rest of the economy, so that changes in that single market can be assumed to have a de minimus effect on the equilibrium of all other markets. (The conditions under which such an assumption could be justified are themselves not unproblematic, but I am now assuming that those problems can in fact be assumed away at least in many applications. And a good empirical economist will have a good instinctual sense for when it’s OK to make the assumption and when it’s not OK to make the assumption.)

So, the underlying assumption of microeconomics is that the individual markets under analysis are very small relative to the whole economy. Why? Because if those markets are not small, we can’t assume that the demand curves, cost curves, and supply curves end up where they started. Because a high price in one market may have effects on other markets and those effects will have further repercussions that move the very demand, cost and supply curves that were drawn to represent the market of interest. If the curves themselves are unstable, the ability to predict the final outcome is greatly impaired if not completely compromised.

The working assumption of the bread and butter partial-equilibrium analysis that constitutes econ 101 is that markets have closed borders. And that assumption is not always valid. If markets have open borders so that there is a lot of spillover between and across markets, the markets can only be analyzed in terms of broader systems of simultaneous equations, not the simplified solutions that we like to draw in two-dimensional space corresponding to intersections of stable supply curves with stable supply curves.

What Keynes was saying is that it makes no sense to draw a curve representing the demand of an entire economy for labor or a curve representing the supply of labor of an entire economy, because the underlying assumption of such curves that all other prices are constant cannot possibly be satisfied when you are drawing a demand curve and a supply curve for an input that generates more than half the income earned in an economy.

But the problem is even deeper than just the inability to draw a curve that meaningfully represents the demand of an entire economy for labor. The assumption that you can model a transition from one point on the curve to another point on the curve is simply untenable, because not only is the assumption that other variables are being held constant untenable and self-contradictory, the underlying assumption that you are starting from an equilibrium state is never satisfied when you are trying to analyze a situation of unemployment – at least if you have enough sense not to assume that economy is starting from, and is not always in, a state of general equilibrium.

So, Keynes was certainly correct to reject the naïve transfer of partial equilibrium theorizing from its legitimate field of applicability in analyzing the effects of small parameter changes on outcomes in individual markets – what later came to be known as comparative statics – to macroeconomic theorizing about economy-wide disturbances in which the assumptions underlying the comparative-statics analysis used in microeconomics are clearly not satisfied. That illegitimate transfer of one kind of theorizing to another has come to be known as the demand for microfoundations in macroeconomic models that is the foundational methodological principle of modern macroeconomics.

The principle, as I have been arguing for some time, is illegitimate for a variety of reasons. And one of those reasons is that microeconomics itself is based on the macroeconomic foundational assumption of a pre-existing general equilibrium, in which all plans in the entire economy are, and will remain, perfectly coordinated throughout the analysis of a particular parameter change in a single market. Once you relax the assumption that all, but one, markets are in equilibrium, the discipline imposed by the assumption of the rationality of general equilibrium and comparative statics is shattered, and a different kind of theorizing must be adopted to replace it.

The search for that different kind of theorizing is the challenge that has always faced macroeconomics. Despite heroic attempts to avoid facing that challenge and pretend that macroeconomics can be built as if it were microeconomics, the search for a different kind of theorizing will continue; it must continue. But it would certainly help if more smart and creative people would join in that search.

Hayek and Temporary Equilibrium






















Roy Radner and the Equilibrium of Plans, Prices and Price Expectations























Correct Foresight, Perfect Foresight, and Intertemporal Equilibrium

In my previous post, I discussed Hayek’s path-breaking insight into the meaning of intertemporal equilibrium. His breakthrough was to see that an equilibrium can be understood not as a stationary state in which nothing changes, but as a state in which decentralized plans are both optimal from the point of view of the individuals formulating the plans and mutually consistent, so that the individually optimal plans, at least potentially, could be simultaneously executed. In the simple one-period model, the plans of individuals extending over a single-period time horizon are constrained by the necessary equality for each agent between the value of all planned purchases and the value of all planned sales in that period. A single-period or stationary equilibrium, if it exists, is characterized by a set of prices such that the optimal plans corresponding to that set of prices such that total amount demanded for each product equals the total amount supplied for each product. Thus, an equilibrium price vector has the property that every individual is choosing optimally based on the choice criteria and the constraints governing the decisions for each individual and that those individually optimal choices are mutually consistent, that mutual consistency being manifested in the equality of the total amount demanded and the total amount supplied of each product in that single period.

The problem posed by the concept of intertemporal equilibrium is how to generalize the single-period notion of an equilibrium as a vector of all the observed prices of goods and services actually traded in that single period into a multi-period concept in which the prices on which optimal choices depend include both the actual prices of goods traded in the current period as well as the prices of goods and services that agents plan to buy or sell only in some future time period. In an intertemporal context, the prices on the basis of which optimal plans are chosen cannot be just those prices at which transactions are being executed in the current period; the relevant set of prices must also include those prices at which transactions already being planned in the current period will be executed. Because even choices about transactions today may depend on the prices at which future transactions will take place, future prices can affect not only future demands and supplies they can also affect current demands and supplies.

But because prices in future periods are typically not observable by individuals in the present, it is not observed — but expected — future prices on the basis of which individual agents are making the optimal choices reflected in their intertemporal plans. And insofar as optimal plans depend on expected future prices, those optimal plans can be mutually consistent only if they are based on the same expected future prices, because if their choices are based on different expected future prices, then it is not possible that all expectations are realized. If the expectations of at least one agent, and probably of many agents, will be disappointed, implying that the plans of at least one and probably of many agents will not be optimized and will have to be revised.

The recognition that the mutual consistency of optimal plans requires individuals to accurately foresee the future prices upon which their optimal choices are based suggested that individual agents must be endowed with remarkable capacities to foresee the future. To assume that all individual agents would be endowed with the extraordinary ability to foresee correctly all the future prices relevant to their optimal choices about their intertemporal plans seemed an exceedingly unrealistic assumption on which to premise an economic model.

This dismissive attitude toward the concept of intertemporal equilibrium and the seemingly related assumption of “perfect foresight” necessary for an intertemporal equilibrium to exist was stridently expressed by Oskar Morgenstern in his famous 1935 article “Perfect Foresight and Economic Equilibrium.”

The impossibly high claims which are attributed to the intellectual efficiency of the economic subject immediately indicate that there are included in this equilibrium system not ordinary men, but rather, at least to one another, exactly equal demi-gods, in case the claim of complete foresight is fulfilled. If this is the case, there is, of course, nothing more to be done. If “full” or “perfect” foresight is to provide the basis of the theory of equilibrium in the strictly specified sense, and in the meaning obviously intended by the economic authors, then, a completely meaningless assumption is being considered. If limitations are introduced in such a way that the perfection of foresight is not reached, then these limitations are to be stated very precisely. They would have to be so narrowly drawn that the fundamental aim of producing ostensibly full rationality of the system by means of high, de facto unlimited, foresight, would be lost. For the theoretical economist, there is no way out of this dilemma. ln this discussion, “full” and “perfect” foresight are not only used synonymously, but both are employed, moreover, in the essentialIy more exact sense of limitlessness. This expression would have to be preferred because with the words “perfect” or “imperfect”, there arise superficial valuations which play no role here at all.

Morgenstern then went on to make an even more powerful attack on the idea of perfect foresight: that the idea is itself self-contradictory. Interestingly, he did so by positing an example that would figure in Morgenstern’s later development of game theory with his collaborator John von Neumann (and, as we now know, with his research assistant who in fact was his mathematical guide and mentor, Abraham Wald, fcredited as a co-author of The Theory of Games and Economic Behavior).

Sherlock Holmes, pursued by his opponent, Moriarity, leaves London for Dover. The train stops at a station on the way, and he alights there rather than traveling on to Dover. He has seen Moriarity at the railway station, recognizes that he is very clever and expects that Moriarity will take a faster special train in order to catch him in Dover. Holmes’ anticipation turns out to be correct. But what if Moriarity had been still more clever, had estimated Holmes’ mental abilities better and had foreseen his actions accordingly? Then, obviously, he would have traveled to the intermediate station. Holmes, again, would have had to calculate that, and he himself would have decided to go on to Dover. Whereupon, Moriarity would again have “reacted” differently. Because of so much thinking they might not have been able to act at all or the intellectually weaker of the two would have surrendered to the other in the Victoria Station, since the whole flight would have become unnecessary. Examples of this kind can be drawn from everywhere. However, chess, strategy, etc. presuppose expert knowledge, which encumbers the example unnecessarily.

One may be easily convinced that here lies an insoluble paradox. And the situation is not improved, but, rather, greatly aggravated if we assume that more than two individuals-as, for example, is the case with exchange-are brought together into a position, which would correspond to the one brought forward here. Always, there is exhibited an endless chain of reciprocally conjectural reactions and counter-reactions. This chain can never be broken by an act of knowledge but always only through an arbitrary act-a resolution. This resolution, again, would have to be foreseen by the two or more persons concerned. The paradox still remains no matter how one attempts to twist or turn things around. Unlimited foresight and economic equilibrium are thus irreconcilable with one another. But can equilibrium really take place with a faulty, heterogeneous foresight, however, it may be disposed? This is the question which arises at once when an answer is sought. One can even say this: has foresight been truly introduced at all into the consideration of equilibrium, or, rather, does not the theorem of equilibrium generally stand in no proven connection with the assumptions about foresight, so that a false assumption is being considered?

As Carlo Zappia has shown, it was probably Morgenstern’s attack on the notion of intertemporal equilibrium and perfect foresight that led Hayek to his classic restatement of the idea in his 1937 paper “Economics and Knowledge.” The point that Hayek clarified in his 1937 version, but had not been clear in his earlier expositions of the concept, is that correct foresight is not an assumption from which the existence of an intertemporal equilibrium can be causally deduced; there is no assertion that a state of equilibrium is the result of correct foresight. Rather, correct foresight is the characteristic that defines what is meant when the term “intertemporal equilibrium” is used in economic theory. Morgenstern’s conceptual error was to mistake a tautological statement about what would have to be true if an intertemporal equilibrium were to obtain for a causal statement about what conditions would bring an intertemporal equilibrium into existence.

The idea of correct foresight does not attribute any special powers to the economic agents who might under hypothetical circumstances possess correct expectations of future prices. The term is not meant to be a description of an actual state of affairs, but a description of what would have to be true for a state of affairs to be an equilibrium state of affairs.

As an aside, I would simply mention that many years ago when I met Hayek and had the opportunity to ask him about his 1937 paper and his role in developing the concept of intertemporal equilibrium, he brought my attention to his 1928 paper in which he first described an intertemporal equilibrium as state of affairs in which agents had correct expectations about future prices. My recollection of that conversation is unfortunately rather vague, but I do remember that he expressed some regret for not having had the paper translated into English, which would have established his priority in articulating the intertemporal equilibrium concept. My recollection is that the reason he gave for not having had the paper translated into English was that there was something about the paper about which he felt dissatisfied, but I can no longer remember what it was that he said he was dissatisfied with. However, I would now be inclined to conjecture that he was dissatisfied with not having disambiguated, as he did in the 1937 paper, between correct foresight as a defining characteristic of what intertemporal equilibrium means versus perfect foresight as the cause that brings intertemporal equilibruim into existence.

It is also interesting to note that the subsequent development of game theory in which Morgenstern played a not insubstantial role, shows that under a probabilistic interpretation of the interaction between Holmes and Moriarity, there could be an optimal mixed strategy that would provide an equilibrium solution of repeated Holmes-Moriarity interactions. But if the interaction is treated as a single non-repeatable event with no mixed strategy available to either party, the correct interpretation of the interaction is certainly that there is no equilibrium solution to the interaction. If there is no equilibrium solution, then it is precisely the absence of an equilibrium solution that implies the impossibility of correct foresight, correct foresight and the existence of an equilibrium being logically equivalent concepts.

Hayek and Intertemporal Equilibrium

I am starting to write a paper on Hayek and intertemporal equilibrium, and as I write it over the next couple of weeks, I am going to post sections of it on this blog. Comments from readers will be even more welcome than usual, and I will do my utmost to reply to comments, a goal that, I am sorry to say, I have not been living up to in my recent posts.

The idea of equilibrium is an essential concept in economics. It is an essential concept in other sciences as well, its meaning in economics is not the same as in other disciplines. The concept having originally been borrowed from physics, the meaning originally attached to it by economists corresponded to the notion of a system at rest, and it took a long time for economists to see that viewing an economy as a system at rest was not the only, or even the most useful, way of applying the equilibrium concept to economic phenomena.

What would it mean for an economic system to be at rest? The obvious answer was to say that prices and quantities would not change. If supply equals demand in every market, and if there no exogenous change introduced into the system, e.g., in population, technology, tastes, etc., it would seem that would be no reason for the prices paid and quantities produced to change in that system. But that view of an economic system was a very restrictive one, because such a large share of economic activity – savings and investment — is predicated on the assumption and expectation of change.

The model of a stationary economy at rest in which all economic activity simply repeats what has already happened before did not seem very satisfying or informative, but that was the view of equilibrium that originally took hold in economics. The idea of a stationary timeless equilibrium can be traced back to the classical economists, especially Ricardo and Mill who wrote about the long-run tendency of an economic system toward a stationary state. But it was the introduction by Jevons, Menger, Walras and their followers of the idea of optimizing decisions by rational consumers and producers that provided the key insight for a more robust and fruitful version of the equilibrium concept.

If each economic agent (household or business firm) is viewed as making optimal choices based on some scale of preferences subject to limitations or constraints imposed by their capacities, endowments, technology and the legal system, then the equilibrium of an economy must describe a state in which each agent, given his own subjective ranking of the feasible alternatives, is making a optimal decision, and those optimal decisions are consistent with those of all other agents. The optimal decisions of each agent must simultaneously be optimal from the point of view of that agent while also being consistent, or compatible, with the optimal decisions of every other agent. In other words, the decisions of all buyers of how much to purchase must be consistent with the decisions of all sellers of how much to sell.

The idea of an equilibrium as a set of independently conceived, mutually consistent optimal plans was latent in the earlier notions of equilibrium, but it could not be articulated until a concept of optimality had been defined. That concept was utility maximization and it was further extended to include the ideas of cost minimization and profit maximization. Once the idea of an optimal plan was worked out, the necessary conditions for the mutual consistency of optimal plans could be articulated as the necessary conditions for a general economic equilibrium. Once equilibrium was defined as the consistency of optimal plans, the path was clear to define an intertemporal equilibrium as the consistency of optimal plans extending over time. Because current goods and services and otherwise identical goods and services in the future could be treated as economically distinct goods and services, defining the conditions for an intertemporal equilibrium was formally almost equivalent to defining the conditions for a static, stationary equilibrium. Just as the conditions for a static equilibrium could be stated in terms of equalities between marginal rates of substitution of goods in consumption and in production to their corresponding price ratios, an intertemporal equilibrium could be stated in terms of equalities between the marginal rates of intertemporal substitution in consumption and in production and their corresponding intertemporal price ratios.

The only formal adjustment required in the necessary conditions for static equilibrium to be extended to intertemporal equilibrium was to recognize that, inasmuch as future prices (typically) are unobservable, and hence unknown to economic agents, the intertemporal price ratios cannot be ratios between actual current prices and actual future prices, but, instead, ratios between current prices and expected future prices. From this it followed that for optimal plans to be mutually consistent, all economic agents must have the same expectations of the future prices in terms of which their plans were optimized.

The concept of an intertemporal equilibrium was first presented in English by F. A. Hayek in his 1937 article “Economics and Knowledge.” But it was through J. R. Hicks’s Value and Capital published two years later in 1939 that the concept became more widely known and understood. In explaining and applying the concept of intertemporal equilibrium and introducing the derivative concept of a temporary equilibrium in which current markets clear, but individual expectations of future prices are not the same, Hicks did not claim originality, but instead of crediting Hayek for the concept, or even mentioning Hayek’s 1937 paper, Hicks credited the Swedish economist Erik Lindahl, who had published articles in the early 1930s in which he had articulated the concept. But although Lindahl had published his important work on intertemporal equilibrium before Hayek’s 1937 article, Hayek had already explained the concept in a 1928 article “Das intertemporale Gleichgewichtasystem der Priese und die Bewegungen des ‘Geltwertes.'” (English translation: “Intertemporal price equilibrium and movements in the value of money.“)

Having been a junior colleague of Hayek’s in the early 1930s when Hayek arrived at the London School of Economics, and having come very much under Hayek’s influence for a few years before moving in a different theoretical direction in the mid-1930s, Hicks was certainly aware of Hayek’s work on intertemporal equilibrium, so it has long been a puzzle to me why Hicks did not credit Hayek along with Lindahl for having developed the concept of intertemporal equilibrium. It might be worth pursuing that question, but I mention it now only as an aside, in the hope that someone else might find it interesting and worthwhile to try to find a solution to that puzzle. As a further aside, I will mention that Murray Milgate in a 1979 article “On the Origin of the Notion of ‘Intertemporal Equilibrium’” has previously tried to redress the failure to credit Hayek’s role in introducing the concept of intertemporal equilibrium into economic theory.

What I am going to discuss in here and in future posts are three distinct ways in which the concept of intertemporal equilibrium has been developed since Hayek’s early work – his 1928 and 1937 articles but also his 1941 discussion of intertemporal equilibrium in The Pure Theory of Capital. Of course, the best known development of the concept of intertemporal equilibrium is the Arrow-Debreu-McKenzie (ADM) general-equilibrium model. But although it can be thought of as a model of intertemporal equilibrium, the ADM model is set up in such a way that all economic decisions are taken before the clock even starts ticking; the transactions that are executed once the clock does start simply follow a pre-determined script. In the ADM model, the passage of time is a triviality, merely a way of recording the sequential order of the predetermined production and consumption activities. This feat is accomplished by assuming that all agents are present at time zero with their property endowments in hand and capable of transacting – but conditional on the determination of an equilibrium price vector that allows all optimal plans to be simultaneously executed over the entire duration of the model — in a complete set of markets (including state-contingent markets covering the entire range of contingent events that will unfold in the course of time whose outcomes could affect the wealth or well-being of any agent with the probabilities associated with every contingent event known in advance).

Just as identical goods in different physical locations or different time periods can be distinguished as different commodities that cn be purchased at different prices for delivery at specific times and places, identical goods can be distinguished under different states of the world (ice cream on July 4, 2017 in Washington DC at 2pm only if the temperature is greater than 90 degrees). Given the complete set of state-contingent markets and the known probabilities of the contingent events, an equilibrium price vector for the complete set of markets would give rise to optimal trades reallocating the risks associated with future contingent events and to an optimal allocation of resources over time. Although the ADM model is an intertemporal model only in a limited sense, it does provide an ideal benchmark describing the characteristics of a set of mutually consistent optimal plans.

The seminal work of Roy Radner in relaxing some of the extreme assumptions of the ADM model puts Hayek’s contribution to the understanding of the necessary conditions for an intertemporal equilibrium into proper perspective. At an informal level, Hayek was addressing the same kinds of problems that Radner analyzed with far more powerful analytical tools than were available to Hayek. But the were both concerned with a common problem: under what conditions could an economy with an incomplete set of markets be said to be in a state of intertemporal equilibrium? In an economy lacking the full set of forward and state contingent markets describing the ADM model, intertemporal equilibrium cannot predetermined before trading even begins, but must, if such an equilibrium obtains, unfold through the passage of time. Outcomes might be expected, but they would not be predetermined in advance. Echoing Hayek, though to my knowledge he does not refer to Hayek in his work, Radner describes his intertemporal equilibrium under uncertainty as an equilibrium of plans, prices, and price expectations. Even if it exists, the Radner equilibrium is not the same as the ADM equilibrium, because without a full set of markets, agents can’t fully hedge against, or insure, all the risks to which they are exposed. The distinction between ex ante and ex post is not eliminated in the Radner equilibrium, though it is eliminated in the ADM equilibrium.

Additionally, because all trades in the ADM model have been executed before “time” begins, it seems impossible to rationalize holding any asset whose only use is to serve as a medium of exchange. In his early writings on business cycles, e.g., Monetary Theory and the Trade Cycle, Hayek questioned whether it would be possible to rationalize the holding of money in the context of a model of full equilibrium, suggesting that monetary exchange, by severing the link between aggregate supply and aggregate demand characteristic of a barter economy as described by Say’s Law, was the source of systematic deviations from the intertemporal equilibrium corresponding to the solution of a system of Walrasian equations. Hayek suggested that progress in analyzing economic fluctuations would be possible only if the Walrasian equilibrium method could be somehow be extended to accommodate the existence of money, uncertainty, and other characteristics of the real world while maintaining the analytical discipline imposed by the equilibrium method and the optimization principle. It proved to be a task requiring resources that were beyond those at Hayek’s, or probably anyone else’s, disposal at the time. But it would be wrong to fault Hayek for having had to insight to perceive and frame a problem that was beyond his capacity to solve. What he may be criticized for is mistakenly believing that he he had in fact grasped the general outlines of a solution when in fact he had only perceived some aspects of the solution and offering seriously inappropriate policy recommendations based on that seriously incomplete understanding.

In Value and Capital, Hicks also expressed doubts whether it would be possible to analyze the economic fluctuations characterizing the business cycle using a model of pure intertemporal equilibrium. He proposed an alternative approach for analyzing fluctuations which he called the method of temporary equilibrium. The essence of the temporary-equilibrium method is to analyze the behavior of an economy under the assumption that all markets for current delivery clear (in some not entirely clear sense of the term “clear”) while understanding that demand and supply in current markets depend not only on current prices but also upon expected future prices, and that the failure of current prices to equal what they had been expected to be is a potential cause for the plans that economic agents are trying to execute to be modified and possibly abandoned. In the Pure Theory of Capital, Hayek discussed Hicks’s temporary-equilibrium method a possible method of achieving the modification in the Walrasian method that he himself had proposed in Monetary Theory and the Trade Cycle. But after a brief critical discussion of the method, he dismissed it for reasons that remain obscure. Hayek’s rejection of the temporary-equilibrium method seems in retrospect to have been one of Hayek’s worst theoretical — or perhaps, meta-theoretical — blunders.

Decades later, C. J. Bliss developed the concept of temporary equilibrium to show that temporary equilibrium method can rationalize both holding an asset purely for its services as a medium of exchange and the existence of financial intermediaries (private banks) that supply financial assets held exclusively to serve as a medium of exchange. In such a temporary-equilibrium model with financial intermediaries, it seems possible to model not only the existence of private suppliers of a medium of exchange, but also the conditions – in a very general sense — under which the system of financial intermediaries breaks down. The key variable of course is vectors of expected prices subject to which the plans of individual households, business firms, and financial intermediaries are optimized. The critical point that emerges from Bliss’s analysis is that there are sets of expected prices, which if held by agents, are inconsistent with the existence of even a temporary equilibrium. Thus price flexibility in current market cannot, in principle, result in even a temporary equilibrium, because there is no price vector of current price in markets for present delivery that solves the temporary-equilibrium system. Even perfect price flexibility doesn’t lead to equilibrium if the equilibrium does not exist. And the equilibrium cannot exist if price expectations are in some sense “too far out of whack.”

Expected prices are thus, necessarily, equilibrating variables. But there is no economic mechanism that tends to cause the adjustment of expected prices so that they are consistent with the existence of even a temporary equilibrium, much less a full equilibrium.

Unfortunately, modern macroeconomics continues to neglect the temporary-equilibrium method; instead macroeconomists have for the most part insisted on the adoption of the rational-expectations hypothesis, a hypothesis that elevates question-begging to the status of a fundamental axiom of rationality. The crucial error in the rational-expectations hypothesis was to misunderstand the role of the comparative-statics method developed by Samuelson in The Foundations of Economic Analysis. The role of the comparative-statics method is to isolate the pure theoretical effect of a parameter change under a ceteris-paribus assumption. Such an effect could be derived only by comparing two equilibria under the assumption of a locally unique and stable equilibrium before and after the parameter change. But the method of comparative statics is completely inappropriate to most macroeconomic problems which are precisely concerned with the failure of the economy to achieve, or even to approximate, the unique and stable equilibrium state posited by the comparative-statics method.

Moreover, the original empirical application of the rational-expectations hypothesis by Muth was in the context of the behavior of a single market in which the market was dominated by well-informed specialists who could be presumed to have well-founded expectations of future prices conditional on a relatively stable economic environment. Under conditions of macroeconomic instability, there is good reason to doubt that the accumulated knowledge and experience of market participants would enable agents to form accurate expectations of the future course of prices even in those markets about which they expert knowledge. Insofar as the rational expectations hypothesis has any claim to empirical relevance it is only in the context of stable market situations that can be assumed to be already operating in the neighborhood of an equilibrium. For the kinds of problems that macroeconomists are really trying to answer that assumption is neither relevant nor appropriate.

A Primer on Equilibrium

After my latest post about rational expectations, Henry from Australia, one of my most prolific commenters, has been engaging me in a conversation about what assumptions are made – or need to be made – for an economic model to have a solution and for that solution to be characterized as an equilibrium, and in particular, a general equilibrium. Equilibrium in economics is not always a clearly defined concept, and it can have a number of different meanings depending on the properties of a given model. But the usual understanding is that the agents in the model (as consumers or producers) are trying to do as well for themselves as they can, given the endowments of resources, skills and technology at their disposal and given their preferences. The conversation was triggered by my assertion that rational expectations must be “compatible with the equilibrium of the model in which those expectations are embedded.”

That was the key insight of John Muth in his paper introducing the rational-expectations assumption into economic modelling. So in any model in which the current and future actions of individuals depend on their expectations of the future, the model cannot arrive at an equilibrium unless those expectations are consistent with the equilibrium of the model. If the expectations of agents are incompatible or inconsistent with the equilibrium of the model, then, since the actions taken or plans made by agents are based on those expectations, the model cannot have an equilibrium solution.

Now Henry thinks that this reasoning is circular. My argument would be circular if I defined an equilibrium to be the same thing as correct expectations. But I am not so defining an equilibrium. I am saying that the correctness of expectations by all agents implies 1) that their expectations are mutually consistent, and 2) that, having made plans, based on their expectations, which, by assumption, agents felt were the best set of choices available to them given those expectations, if the expectations of the agents are realized, then they would not regret the decisions and the choices that they made. Each agent would be as well off as he could have made himself, given his perceived opportunities when the decision were made. That the correctness of expectations implies equilibrium is the consequence of assuming that agents are trying to optimize their decision-making process, given their available and expected opportunities. If all expected opportunities are correctly foreseen, then all decisions will have been the optimal decisions under the circumstances. But nothing has been said that requires all expectations to be correct, or even that it is possible for all expectations to be correct. If an equilibrium does not exist, and just because you can write down an economic model, it does not mean that a solution to the model exists, then the sweet spot where all expectations are consistent and compatible is just a blissful fantasy. So a logical precondition to showing that rational expectations are even possible is to prove that an equilibrium exists. There is nothing circular about the argument.

Now the key to proving the existence of a general equilibrium is to show that the general equilibrium model implies the existence of what mathematicians call a fixed point. A fixed point is said to exist when there is a mapping – a rule or a function – that takes every point in a convex compact set of points and assigns that point to another point in the same set. A convex, compact set has two important properties: 1) the line connecting any two points in the set is entirely contained within the boundaries of the set, and 2) there are no gaps between any two points in set. The set of points in a circle or a rectangle is a convex compact set; the set of points contained in the Star of David is not a convex set. Any two points in the circle will be connected by a line that lies completely within the circle; the points at adjacent edges of a Star of David will be connected by a line that lies entirely outside the Star of David.

If you think of the set of all possible price vectors for an economy, those vectors – each containing a price for each good or service in the economy – could be mapped onto itself in the following way. Given all the equations describing the behavior of each agent in the economy, the quantity demanded and supplied of each good could be calculated, giving us the excess demand (the difference between amount demand and supplied) for each good. Then the price of every good in excess demand would be raised, the price of every good in negative excess demand would be reduced, and the price of every good with zero excess demand would be held constant. To ensure that the mapping was taking a point from a given convex set onto itself, all prices could be normalized so that they would have the property that the sum of all the individual prices would always equal 1. The fixed point theorem ensures that for a mapping from one convex compact set onto itself there must be at least one fixed point, i.e., at least one point in the set that gets mapped onto itself. The price vector corresponding to that point is an equilibrium, because, given how our mapping rule was defined, a point would be mapped onto itself if and only if all excess demands are zero, so that no prices changed. Every fixed point – and there may be one or more fixed points – corresponds to an equilibrium price vector and every equilibrium price vector is associated with a fixed point.

Before going on, I ought to make an important observation that is often ignored. The mathematical proof of the existence of an equilibrium doesn’t prove that the economy operates at an equilibrium, or even that the equilibrium could be identified under the mapping rule described (which is a kind of formalization of the Walrasian tatonnement process). The mapping rule doesn’t guarantee that you would ever discover a fixed point in any finite amount of iterations. Walras thought the price adjustment rule of raising the prices of goods in excess demand and reducing prices of goods in excess supply would converge on the equilibrium price vector. But the conditions under which you can prove that the naïve price-adjustment rule converges to an equilibrium price vector turn out to be very restrictive, so even though we can prove that the competitive model has an equilibrium solution – in other words the behavioral, structural and technological assumptions of the model are coherent, meaning that the model has a solution, the model has no assumptions about how prices are actually determined that would prove that the equilibrium is ever reached. In fact, the problem is even more daunting than the previous sentence suggest, because even Walrasian tatonnement imposes an incredibly powerful restriction, namely that no trading is allowed at non-equilibrium prices. In practice there are almost never recontracting provisions allowing traders to revise the terms of their trades once it becomes clear that the prices at which trades were made were not equilibrium prices.

I now want to show how price expectations fit into all of this, because the original general equilibrium models were either one-period models or formal intertemporal models that were reduced to single-period models by assuming that all trading for future delivery was undertaken in the first period by long-lived agents who would eventually carry out the transactions that were contracted in period 1 for subsequent consumption and production. Time was preserved in a purely formal, technical way, but all economic decision-making was actually concluded in the first period. But even though the early general-equilibrium models did not encompass expectations, one of the extraordinary precursors of modern economics, Augustin Cournot, who was way too advanced for his contemporaries even to comprehend, much less make any use of, what he was saying, had incorporated the idea of expectations into the solution of his famous economic model of oligopolistic price setting.

The key to oligopolistic pricing is that each oligopolist must take into account not just consumer demand for his product, and his own production costs; he must consider as well what actions will be taken by his rivals. This is not a problem for a competitive producer (a price-taker) or a pure monopolist. The price-taker simply compares the price at which he can sell as much as he wants with his production costs and decides how much it is worthwhile to produce by comparing his marginal cost to price ,and increases output until the marginal cost rises to match the price at which he can sell. The pure monopolist, if he knows, as is assumed in such exercises, or thinks he knows the shape of the customer demand curve, selects the price and quantity combination on the demand curve that maximizes total profit (corresponding to the equality of marginal revenue and marginal cost). In oligopolistic situations, each producer must take into account how much his rivals will sell, or what prices they will set.

It was by positing such a situation and finding an analytic solution, that Cournot made a stunning intellectual breakthrough. In the simple duopoly case, Cournot posited that if the duopolists had identical costs, then each could find his optimal price conditional on the output chosen by the other. This is a simple profit-maximization problem for each duopolist, given a demand curve for the combined output of both (assumed to be identical, so that a single price must obtain for the output of both) a cost curve and the output of the other duopolist. Thus, for each duopolist there is a reaction curve showing his optimal output given the output of the other. See the accompanying figure.cournot

If one duopolist produces zero, the optimal output for the other is the monopoly output. Depending on what the level of marginal cost is, there is some output by either of the duopolists that is sufficient to make it unprofitable for the other duopolist to produce anything. That level of output corresponds to the competitive output where price just equals marginal cost. So the slope of the two reaction functions corresponds to the ratio of the monopoly output to the competitive output, which, with constant marginal cost is 2:1. Given identical costs, the two reaction curves are symmetric and the optimal output for each, given the expected output of the other, corresponds to the intersection of the two reaction curves, at which both duopolists produce the same quantity. The combined output of the two duopolists will be greater than the monopoly output, but less than the competitive output at which price equals marginal cost. With constant marginal cost, it turns out that each duopolist produces one-third of the competitive output. In the general case with n oligoplists, the ratio of the combined output of all n firms to the competitive output equals n/(n+1).

Cournot’s solution corresponds to a fixed point where the equilibrium of the model implies that both duopolists have correct expectations of the output of the other. Given the assumptions of the model, if the duopolists both expect the other to produce an output equal to one-third of the competitive output, their expectations will be consistent and will be realized. If either one expects the other to produce a different output, the outcome will not be an equilibrium, and each duopolist will regret his output decision, because the price at which he can sell his output will differ from the price that he had expected. In the Cournot case, you could define a mapping of a vector of the quantities that each duopolist had expected the other to produce and the corresponding planned output of each duopolist. An equilibrium corresponds to a case in which both duopolists expected the output planned by the other. If either duopolist expected a different output from what the other planned, the outcome would not be an equilibrium.

We can now recognize that Cournot’s solution anticipated John Nash’s concept of an equilibrium strategy in which player chooses a strategy that is optimal given his expectation of what the other player’s strategy will be. A Nash equilibrium corresponds to a fixed point in which each player chooses an optimal strategy based on the correct expectation of what the other player’s strategy will be. There may be more than one Nash equilibrium in many games. For example, rather than base their decisions on an expectation of the quantity choice of the other duopolist, the two duopolists could base their decisions on an expectation of what price the other duopolist would set. In the constant-cost case, this choice of strategies would lead to the competitive output because both duopolists would conclude that the optimal strategy of the other duopolist would be to charge a price just sufficient to cover his marginal cost. This was the alternative oligopoly model suggested by another French economist J. L. F. Bertrand. Of course there is a lot more to be said about how oligopolists strategize than just these two models, and the conditions under which one or the other model is the more appropriate. I just want to observe that assumptions about expectations are crucial to how we analyze market equilibrium, and that the importance of these assumptions for understanding market behavior has been recognized for a very long time.

But from a macroeconomic perspective, the important point is that expected prices become the critical equilibrating variable in the theory of general equilibrium and in macroeconomics in general. Single-period models of equilibrium, including general-equilibrium models that are formally intertemporal, but in which all trades are executed in the initial period at known prices in a complete array of markets determining all future economic activity, are completely sterile and useless for macroeconomics except as a stepping stone to analyzing the implications of imperfect forecasts of future prices. If we want to think about general equilibrium in a useful macroeconomic context, we have to think about a general-equilibrium system in which agents make plans about consumption and production over time based on only the vaguest conjectures about what future conditions will be like when the various interconnected stages of their plans will be executed.

Unlike the full Arrow-Debreu system of complete markets, a general-equilibrium system with incomplete markets cannot be equilibrated, even in principle, by price adjustments in the incomplete set of present markets. Equilibration depends on the consistency of expected prices with equilibrium. If equilibrium is characterized by a fixed point, the fixed point must be mapping of a set of vectors of current prices and expected prices on to itself. That means that expected future prices are as much equilibrating variables as current market prices. But expected future prices exist only in the minds of the agents, they are not directly subject to change by market forces in the way that prices in actual markets are. If the equilibrating tendencies of market prices in a system of complete markets are very far from completely effective, the equilibrating tendencies of expected future prices may not only be non-existent, but may even be potentially disequilibrating rather than equilibrating.

The problem of price expectations in an intertemporal general-equilibrium system is central to the understanding of macroeconomics. Hayek, who was the father of intertemporal equilibrium theory, which he was the first to outline in a 1928 paper in German, and who explained the problem with unsurpassed clarity in his 1937 paper “Economics and Knowledge,” unfortunately did not seem to acknowledge its radical consequences for macroeconomic theory, and the potential ineffectiveness of self-equilibrating market forces. My quarrel with rational expectations as a strategy of macroeconomic analysis is its implicit assumption, lacking any analytical support, that prices and price expectations somehow always adjust to equilibrium values. In certain contexts, when there is no apparent basis to question whether a particular market is functioning efficiently, rational expectations may be a reasonable working assumption for modelling observed behavior. However, when there is reason to question whether a given market is operating efficiently or whether an entire economy is operating close to its potential, to insist on principle that the rational-expectations assumption must be made, to assume, in other words, that actual and expected prices adjust rapidly to their equilibrium values allowing an economy to operate at or near its optimal growth path, is simply, as I have often said, an exercise in circular reasoning and question begging.

Price Stickiness Is a Symptom not a Cause



Then a bit later, Nick continues:
















Thinking about Interest and Irving Fisher

In two recent posts I have discussed Keynes’s theory of interest and the natural rate of interest. My goal in both posts was not to give my own view of the correct way to think about what determines interest rates,  but to identify and highlight problems with Keynes’s liquidity-preference theory of interest, and with the concept of a natural rate of interest. The main point that I wanted to make about Keynes’s liquidity-preference theory was that although Keynes thought that he was explaining – or perhaps, explicating — the rate of interest, his theory was nothing more than an explanation of why, typically, the nominal pecuniary yield on holding cash is less than the nominal yield on holding real assets, the difference in yield being attributable to the liquidity services derived from holding a maximally liquid asset rather than holding an imperfectly liquid asset. Unfortunately, Keynes imagined that by identifying and explaining the liquidity premium on cash, he had thereby explained the real yield on holding physical capital assets; he did nothing of the kind, as the marvelous exposition of the theory of own rates of interest in chapter 17 of the General Theory unwittingly demonstrates.

For expository purposes, I followed Keynes in contrasting his liquidity-preference theory with what he called the classical theory of interest, which he identified with Alfred Marshall, in which the rate of interest is supposed to be the rate that equilibrates saving and investment. I criticized Keynes for attributing this theory to Marshall rather than to Irving Fisher, which was, I am now inclined to think, a mistake on my part, because I doubt, based on a quick examination of Fisher’s two great books The Rate of Interest and The Theory of Interest, that he ever asserted that the rate of interest is determined by equilibrating savings and investment. (I actually don’t know if Marshall did or did make such an assertion.) But I think it’s clear that Fisher did not formulate his theory in terms of equating investment and savings via adjustments in the rate of interest rate. Fisher, I think, did agree (but I can’t quote a passage to this effect) that savings and investment are equal in equilibrium, but his analysis of the determination of the rate of interest was not undertaken in terms of equalizing two flows, i.e., savings and investment. Instead the analysis was carried out in terms of individual or household decisions about how much to consume out of current and expected future income, and in terms of decisions by business firms about how much available resources to devote to producing output for current consumption versus producing for future consumption. Fisher showed (in Walrasian fashion) that there are exactly enough equations in his system to solve for all the independent variables, so that his system had a solution. (That Walrasian argument of counting equations and unknowns is mathematically flawed, but later work by my cousin Abraham Wald and subsequently by Arrow, Debreu and McKenzie showed that Fisher’s claim could, under some more or less plausible assumptions, be proved in a mathematically rigorous way.)

Maybe it was Knut Wicksell who in his discussions of the determination of the rate of interest argued that the rate of interest is responsible for equalizing savings and investment, but that was not how Fisher understood what the rate of interest is all about. The Wicksellian notion that the equilibrium rate of interest equalizes savings and investment was thus a misunderstanding of the Fisherian theory, and it would be a worthwhile endeavor to trace the genesis and subsequent development of this misunderstanding to the point that Keynes and his contemporaries could have thought that they were giving an accurate representation of what orthodox theory asserted when they claimed that according to orthodox theory the rate of interest is what ensures equality between savings and investment.

This mistaken doctrine was formalized as the loanable-funds theory of interest – I believe that Dennis Robertson is usually credited with originating this term — in which savings is represented as the supply of loanable funds and investment is represented as the demand for loanable funds, with the rate of interest serving as a sort of price that is determined in Marshallian fashion by the intersection of the two schedules. Somehow it became accepted that the loanable-funds doctrine is the orthodox theory of interest determination, but it is clear from Fisher and from standard expositions of the neoclassical theory of interest which are of course simply extensions of Fisher’s work) that the loanable-funds theory is mistaken and misguided at a very basic level. (At this point, I should credit George Blackford for his comments on my post about Keynes’s theory of the rate of interest for helping me realize that it is not possible to make any sense out of the loanable-funds theory even though I am not sure that we agree on exactly why the loanable funds theory doesn’t make sense. Not that I had espoused the loanable-funds theory, but I did not fully appreciate its incoherence.)

Why do I say that the loanable-funds theory is mistaken and incoherent? Simply because it is fundamentally inconsistent with the essential properties of general-equilibrium analysis. In general-equilibrium analysis, interest rates emerge not as a separate subset of prices determined in a corresponding subset of markets; they emerge from the intertemporal relationships between and across all asset markets and asset prices. To view the rate of interest as being determined in a separate market for loanable funds as if the rate of interest were not being simultaneously determined in all asset markets is a complete misunderstanding of the theory of intertemporal general equilibrium.

Here’s how Fisher put over a century ago in The Rate of Interest:

We thus need to distinguish between interest in terms of money and interest in terms of goods. The first thought suggested by this fact is that the rate of interest in money is “nominal” and that in goods “real.” But this distinction is not sufficient, for no two forms of goods maintain or are expected to maintain, a constant price ratio toward each other. There are therefore just as many rates of interest in goods as there are forms of goods diverging in value. (p. 84, Fisher’s emphasis).

So a quarter of a century before Sraffa supposedly introduced the idea of own rates of interest in his 1932 review of Hayek’s Prices and Production, Fisher had done so in his first classic treatise on interest, which reproduced the own-rate analysis in his 1896 monograph Appreciation and Interest. While crediting Sraffa for introducing the concept of own rates of interest, Keynes, in chapter 17, simply — and brilliantly extends the basics of Fisher’s own-rate analysis, incorporating the idea of liquidity preference and silently correcting Sraffa insofar as his analysis departed from Fisher’s.

Christopher Bliss in his own classic treatise on the theory of interest, expands upon Fisher’s point.

According to equilibrium theory – according indeed to any theory of economic action which relates firms’ decisions to prospective profit and households’ decisions to budget-constrained searches for the most preferred combination of goods – it is prices which play the fundamental role. This is because prices provide the weights to be attached to the possible amendments to their net supply plans which the actors have implicitly rejected in deciding upon their choices. In an intertemporal economy it is then, naturally, present-value prices which play the fundamental role. Although this argument is mounted here on the basis of a consideration of an economy with forward markets in intertemporal equilibrium, it in no way depends on this particular foundation. As has been remarked, if forward markets are not in operation the economic actors have no choice but to substitute their “guesses” for the firm quotations of the forward markets. This will make a big difference, since full intertemporal equilibrium is not likely to be achieved unless there is a mechanism to check and correct for inconsistency in plans and expectations. But the forces that pull economic decisions one way or another are present-value prices . . . be they guesses or firm quotations. (pp. 55-56)

Changes in time preference therefore cause immediate changes in the present value prices of assets thereby causing corresponding changes in own rates of interest. Changes in own rates of interest constrain the rates of interest charged on money loans; changes in asset valuations and interest rates induce changes in production, consumption plans and the rate at which new assets are produced and capital accumulated. The notion that there is ever a separate market for loanable funds in which the rate of interest is somehow determined, and savings and investment are somehow equilibrated is simply inconsistent with the basic Fisherian theory of the rate of interest.

Just as Nick Rowe argues that there is no single market in which the exchange value of money (medium of account) is determined, because money is exchanged for goods in all markets, there can be no single market in which the rate of interest is determined because the value of every asset depends on the rate of interest at which the expected income or service-flow derived from the asset is discounted. The determination of the rate of interest can’t be confined to a single market.

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David Glasner
Washington, DC




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