Document Type


Publication Date



The marginalist revolution in economics became the foundation for the modern regulatory State with its “mixed” economy. Marginalism, whose development defines the boundary between classical political economy and neoclassical economics, completely overturned economists’ theory of value. It developed in the late nineteenth century in England, the Continent and the United States. For the classical political economists, value was a function of past averages. One good example is the wage-fund theory, which saw the optimal rate of wages as a function of the firm’s ability to save from previous profits. Another is the theory of corporate finance, which assessed a corporation’s worth by looking at how much capital had been paid in. Marginalism substituted forwarded looking theories based on the expectations of a rational person about firm and market performance. The optimal rate of wages became the laborer’s expected contribution to the value of the employer; and the value of the corporation became the firm’s anticipated profits. Marginalism swept through university economics in the United States, and by 1920 or so virtually every academic economist was a marginalist.

As a theory of value, marginalism was much more realistic than classical political economy about how market actors behave. At the same time, however, valuations based on expectations about the future, which necessarily included risk, required both more technical analysis and the accommodation of more uncertainty. These changes had a powerful effect on the development of modern regulatory policy in the United States.

Marginalism upended many of the classical conceptions about markets, including assumptions about their robustness, as well as the need for regulation and the optimal type. For regulatory policy the most important issues were: (1) The fixed-cost controversy and the scope of natural monopoly; (2) cost classification, incentives, and ratemaking; (3) the changing domain of market failure; (4) market diversity and the rise of sector regulation; (5) deregulation; (6) concerns about the distribution of wealth; and (7) the assessment of risk. The final section examines risk management under marginalism by looking at two diverse but important areas: negligence and products liability in tort law, and administrative review of patents by the Patent Trial and Appeal Board.