Tag: rational behaviour

A recent article on this blog discussed the likelihood that we will soon move to a cashless society. It is therefore interesting to consider the implications that this might have for consumer behaviour. We might expect the form of payment to make no difference to a rational consumer. However, there is considerable evidence to suggest that this is not the case.

One reason why people appear to spend more freely on credit cards is payment decoupling – you get utility from the item purchased before you pay the cost. However, more recent evidence suggests that this is not the only relevant factor. It appears that the degree of transparency of the payment method also has an effect. Psychologists quoted in the above article conclude from their experimental evidence that:

Payment modes differ in the transparency with which individuals can feel the outflow of money. ….with cash being the most transparent payment mode.

This effect also appears to make people spend cash less freely.

The author of the above article spent some time experimenting with trying to make all his purchases using cash. He found that by doing so, he was able to reduce his spending by about 10%. However, this seems likely to become harder to do in the future and, as the article concludes, it is already difficult to purchase some items with cash.


Why does foreign money seem like play money? Science Codex (04/06/07)


  1. What type of products is it already difficult to purchase with cash?
  2. How did the psychologists test the transparency of payment methods?
  3. Do you think the consumer behaviour described above is likely to persist in the long-run?
  4. Might firms be able to take advantage of the consumers behave described above?
  5. Do you think the transparency of foreign currencies is the main reason why people spend more when they are abroad?

A key economic principle is that rational decision making requires thinking at the margin. This involves a comparison of the additional (or marginal) benefits and costs of an activity.

An example of such rational behaviour would be deciding to drink one more beer or spending one more hour studying only if the additional benefits were greater than the additional costs. The optimum is where marginal benefit equals marginal cost.

And this applies to firms too. A firm maximises its profits by producing the output at which marginal revenue is equal to marginal cost.

However, a recent book by the American business guru Clayton Christensen argues that thinking in this way can be a problem. A recent article in the Guardian describes a story he tells of the time he refused to play for his university basketball team in a national final which took place on a Sunday and therefore conflicted with his religious beliefs. His decision involved sticking to his principles rather than thinking at the margin. For him, whilst the marginal cost of sacrificing these principles just once may well have been small compared to the resulting benefits, the eventual cost would be much higher.

Christensen also suggests that similar arguments can apply to firm decision making. The above article provides an example he uses of decisions made by executives at the Blockbuster video chain. When smaller rivals started offering movies by mail, Blockbuster instead continued to invest in its existing video store business model. This eventually proved disastrous for the company. The explanation given for this is that building on previous investments made more sense than setting up a mail-order arm which would cannibalise their existing business. On the other hand, an alternative explanation may be that executives at Blockbuster were irrationally allowing sunk costs to affect their decision making.


Clayton Christensen’s “How Will You Measure Your Life?” Harvard Business School, Clayton Christensen (9/5/12)
Clay Christensen’s life lessons BloombergBusinessweek, Bradford Wieners (3/5/12)
Bust Blockbuster goes on the block Guardian, Ben Child (4/4/11)


  1. Can you think of a situation where you have decided to stick to your principles rather than think at the margin?
  2. Why does a firm maximise profit by producing the output at which marginal revenue is equal to marginal cost?
  3. What do you think are the main costs of setting up a mail-order business?
  4. Are these costs mainly fixed or variable costs?
  5. Why is it irrational to take sunk costs into account when making a decision?
  6. Can you think of a situation where you have been influenced by sunk costs?

In 2009, Nudge: Improving Decisions about Health, Wealth, and Happiness was published. This book by Richard Thaler and Cass R. Sunstein examines how people are influenced to make decisions or change behaviour.

According to Thaler and Sunstein, people can be ‘nudged’ to change their behaviour. For example, healthy food can be placed in a prominent position in a supermarket or healthy snacks at the checkout. Often it is the junk foods that are displayed prominently and unhealthy, but tasty, snacks are found by the checkout. If fashion houses ceased to use ultra thin models, it could reduce the incentive for many girls to under-eat. If kids at school are given stars or smiley faces for turning off lights or picking up litter, they might be more inclined to do so.

The UK government has been investigating the use of ‘nudges’ as a way of changing behaviour, and the House of Lords Science and Technology Committee has been considering the question. It has just published its report, Behaviour Change. The summary of the report states that:

The currently influential book Nudge by Richard Thaler and Cass Sunstein advocates a range of non-regulatory interventions that seek to influence behaviour by altering the context or environment in which people choose, and seek to influence behaviour in ways which people often do not notice. This approach differs from more traditional government attempts to change behaviour, which have either used regulatory interventions or relied on overt persuasion.

The current Government have taken a considerable interest in the use of “nudge interventions”. Consequently, one aim of this inquiry was to assess the evidence-base for the effectiveness of “nudges”. However, we also examined evidence for the effectiveness of other types of policy intervention, regulatory and non-regulatory, and asked whether the Government make good use of the full range of available evidence when seeking to change behaviour.

The report finds that nudges

… used in isolation will often not be effective in changing the behaviour of the population. Instead, a whole range of measures – including some regulatory measures – will be needed to change behaviour in a way that will make a real difference to society’s biggest problems.

So is there, nevertheless, a role for nudges in changing behaviour – albeit alongside other measures? Read the report and the articles below to find out!


Lords report calls for regulation over persuasion to improve public health Wales Online, David Williamson (19/7/11)
Government’s ‘nudge’ approach to health is not enough, according to House of Lords and Work Foundation HR Magazine, David Woods (20/7/11)
How can I tell if I’ve been nudged Independent, Natalie Haynes (20/7/11)
Healthier behaviour plans are nudge in the wrong direction, say peers Guardian, Sarah Boseley (19/7/11)
‘Nudge’ is not enough, it’s true. But we already knew that Guardian, Jonathan Rowson (19/7/11)
Nudge not enough to change lifestyles – peers BBC News, Nick Triggle (19/7/11)
Why a nudge is not enough to change behaviour BBC News, Baroness Julia Neuberger (19/7/11)
House of Lords findings: why green Nudges are not enough The Green Living Blog, Baroness Julia Neuberger (19/7/11)
Lords Science and Technology Sub-Committee publish report on Behaviour Change YouTube, Baroness Julia Neuberger (14/7/11)


Press Release Lords Science and Technology Select Committee (19/7/11)
Behaviour Change Lords Science and Technology Select Committee (online version) (19/7/11)
Behaviour Change Lords Science and Technology Select Committee (PDF version) (19/7/11)


  1. When may a nudge (a) be enough, (b) not be enough to change behaviour?
  2. What instruments does the government have to change behaviour?
  3. Distinguish between a ‘technical’ and an ‘adaptive’ solution to changing behaviour. Give examples.
  4. Why might adaptive solutions provide more of a challenge to policymakers than technical solutions.
  5. Can a nudge ever be transformative?

Economics is about choice – and choices occur in all parts of our lives. One area is personal relationships. Are we making the best of our relationships with family, friends and sexual partners? Increasingly economists are examining human behaviour in such contexts and asking what factors determine our decisions and whether such decisions are rational.

A recent book looks at the economics of marriage and goes under the title of ‘Spousonomics‘. Its authors, Paula Szuchman and Jenny Anderson, use economics “to master love, marriage and dirty dishes”. As they say:


They look at ways in which such resources can be allocated efficiently. They also look at apparently irrational behaviour and seek to explain it in terms of various ‘failures’ (akin to market failures). They also examine how these failures can be rectified to improve relationships.

So is this economics stepping on the toes of relationship counsellors and psychologists? Or is this the legitimate domain of economists seeking to understand how to optimise in the context of scarce resources – including time and patience?

Spousonomics gets to heart of the matter Belfast Telegraph (19/1/11)
Run your marriage with ‘Spousonomics’: A new book says applying economic rules with transform your relationship Mail Online, Lydia Slater (31/1/11)
Spousonomics: How Economics Can Help Figure Out Your Marriage Book Beast (31/1/11)
Spousonomics Lesson #1: Loss Aversion YouTube (15/1/11)
Economist’s Explanation For Why Getting Married Isn’t Rational Huffington Post, Dan Ariely (15/1/11)
How Economics Saved My Marriage Newsweek, Paula Szuchman (30/1/11)
Want your marriage to profit? New York Post, Sara Stewart (29/1/11)

Spousonomics: blog, Paula Szuchman and Jenny Anderson


  1. How would you define ‘rational behaviour’ in a personal relationship?
  2. Why may marriage be a better deal generally for men than for women?
  3. Give some examples of asymmetry of information in marriage and why this may lead to bad decision making?
  4. Give some examples of risk averse and risk loving behaviour in personal relationships?
  5. Why are many actions in marriage apparently irrational? Could such actions be explained if the concept of ‘irrationality’ is redefined?
  6. Why may a simple demand curve help to explain why sexual relationships tend to wane in many marriages?
  7. Why does moral hazard occur in marriage? Does a combination or moral hazard and asymmetry of information help to explain divorce?
  8. Should marriage guidance counsellors study economics?!

You will probably have come across the concept of consumer sovereignty. In the mythical world of perfect markets, producers are at the beck and call of consumers. Firms that are not responsive to consumer demand go out of business. In other words, in order to survive they have to respond to any shifts in consumer demand. These in turn can be the result of changes in tastes, changes in income, changes in the prices of other goods, and so on.

Of course, the real world is not perfect, but it is still often assumed that consumers are powerful in influencing what firms sell and at what prices. Well, firms would much rather be in a position of manipulating consumer tastes and hence the huge amounts spent on advertising and marketing.

And it doesn’t end there. Firms use many pricing practices which, to put it mildly, try to confuse consumers or lure them into buying things by making them think they are getting something much cheaper than they really are. Take the case of airline tickets. Some budget airlines offer tickets at extremely low prices, such as 99p. But if you select such a flight, by the time you get to the final screen where taxes, charges, supplements, luggage, etc. are added, the price could exceed £100! And ask yourself this, when you buy something with 20% off, or when you buy ‘three for the price of two’ how rational was your decision? Did you really want the product? Was the offer really ‘genuine’?

The Office of Fair Trading has recently completed two investigations into pricing. As it stated 14 months ago when the investigations were launched:

The first, into online targeting of advertising and prices will cover behavioural advertising and customised pricing, where prices are individually tailored using information collected about a consumer’s internet use. It is expected that this study will be completed by spring 2010.

The second, into advertising of prices, will consider various pricing practices which may potentially mislead consumers. The study will look in particular, but not exclusively, at how these practices are used online.

The following articles look at some of the practices that firms use to drive sales – practices that deliberately attempt to manipulate the consumer. The assumption of ‘perfect knowledge’ by consumers may be a long way from the truth.

Shoppers lose out on ‘billions’ because of ‘deceitful’ marketing The Telegraph, Harry Wallop (2/12/10)
OFT warns retailers about ‘misleading’ price offers BBC News (2/12/10)
OFT cracks down on price gimmicks Guardian, Rebecca Smithers (2/12/10)
We’re all gulled by special offers BBC News blogs: Peston’s Picks, Robert Peston (2/12/10)

OFT publications
OFT warning on misleading pricing practices, OFT Press Release 124/10 (2/12/10)
OFT launches market studies into advertising and pricing practices, OFT Press Release 126/09 (15/10/09)
Advertising of Prices, Office of Fair Trading, OFT1291 (December 2010)
Advertising of Prices, Office of Fair Trading, project page
Advertising of Prices Study Overview, Office of Fair Trading, video


  1. Explain each of the different types of pricing practice investigated by the OFT.
  2. Which of the pricing practices are the most misleading for customers?
  3. What is meant by ‘invisible price increases’? How can they be used to mislead the consumer?
  4. Why do certain pricing practices make it hard for the Office for National Statistics to work out the rate of inflation?
  5. Explain the new framework the OFT is adopting for ‘prioritising enforcement action’.
  6. If we end up buying something that we didn’t really intend to buy, does this mean that we were being irrational?
  7. Is advertising generally in or against the interest of consumers? Explain your answer