The problem of the ethics of interest is still unresolved after many centuries of discussion; as long as the institution of private property is accepted, the usefulness of borrowing and lending can hardly be denied. In the long historic process of inheritance, widowhood, gain and loss, by which the distribution of the ownership of capital is determined, there is no reason to suppose that the actual ownership of capital falls into the hands of those best able to administer it. Much of the capital of an advanced society, in fact, tends to be owned by elderly widows, simply because of the greater longevity of the female. Society, therefore, needs some machinery for separating the control of capital from its ownership. Financial instruments and financial markets are the principal agency for performing this function. If all securities took the form of stocks or equities, it might be argued that contractual obligations (bonds), and therefore interest as a form of income, would not be necessary. The case for bonds and interest, however, is the case for specialization. There is a demand for many different degrees of ownership and responsibility, and interest-bearing obligations tap a market that would be hard to reach with equity securities; they are also peculiarly well adapted to the obligations of governments. The principal justification for interest and interest-bearing securities is that they provide an easy and convenient way for skilled administrators to control capital that they do not own and for the owners of capital to relinquish its control. The price society pays for this arrangement is interest.

There remains the problem of the socially optimum rate of interest. It could be argued that there is no point in paying any higher price than one needs to and that the rate of interest should be as low as is consistent with the performance of the function of the financial markets. This position, of course, would place all the burden of control of economic fluctuations on the fiscal system, and it is questionable whether this would be acceptable politically.

The ancient problem of “usury,” in the form of the exploitation of the ignorant poor by moneylenders, is still important in many parts of the world. The remedy is the development of adequate financial institutions for the needs of all classes of people rather than the attempt to prohibit or even to limit the taking of interest. The complex structure of lending institutions in a developed society—banks, building societies, land banks, cooperative banks, credit unions, and so on—testifies to the reality of the service that the lender provides and that interest pays for. The democratization of credit—that is, the extension of the power of borrowing to all classes in society—was one of the important social movements of the 20th century.

Analyses of economic distribution appear in David Ricardo, Principles of Political Economy and Taxation (1817, reissued 1981), the classical subsistence theory of wages; Karl Marx, Capital, vol. 1 (1886; originally published in German, 1867), also available in many later editions, treating the process of distribution as pure conflict; John Bates Clark, Distribution of Wealth (1899, reissued 1965), the classic work on marginal productivity theory whereby distribution is viewed as a harmonious process in which the factors of production receive as income what they contribute to the product; Frank H. Knight, Risk, Uncertainty, and Profit (1921, reprinted 1985), an analysis of profits viewed as a result of imperfect foresight and as a remuneration for risk-bearing; Joseph Schumpeter, The Theory of Economic Development (1934, reprinted 1987; originally published in German, 1912), an analysis of economic development as a result of the innovations of entrepreneurs motivated by profit; Paul H. Douglas, The Theory of Wages (1934, reissued 1964), marginalist theory based on statistical research which sets forth the famous Cobb–Douglas function; K.J. Arrow et al., “Capital–Labor Substitution and Economic Efficiency,” The Review of Economics and Statistics, 43:225–250 (1961), an econometric study explaining the falling share of capital in the national income by the elasticity of substitution; J.R. Hicks, The Theory of Wages, 2nd ed. (1963, reissued 1973), a sophisticated treatment of marginal productivity theory; and Nicholas Kaldor, “Alternative Theories of Distribution,” in his Essays on Value and Distribution, 2nd ed. (1980), a discussion of various theories from Ricardo to Keynes. Dan Usher, The Economic Prerequisite to Democracy (1981), suggests that democracy requires broad agreement on how an economic system will distribute wealth. Other works in this area are Alan S. Blinder, Toward an Economic Theory of Income Distribution (1974); and Ronald G. Ehrenberg and Robert S. Smith, Modern Labor Economics: Theory and Public Policy, 5th ed. (1994).