For it may be that it is the greatest of the own rates of interest (as we may call them) which rules the roost (because it is the greatest of these rates that the marginal efficiency of a capital asset must attain if it is to be newly produced); and that there are reasons why it is the money rate of interest which is often the greatest (because, as we shall find, certain forces, which operate to reduce the own rates of interest of other assets, do not operate in the case of money).