While at Arthur D. Little, Black began thinking seriously about
monetary policy. The major question at the time was between two schools of economic thought, the
Keynesians and
monetarists. The Keynesians (under the leadership of
Franco Modigliani) believe there is a natural tendency of the credit markets toward instability, toward boom and bust, and they assign both monetary and
fiscal policy roles in damping down this cycle, working toward the goal of smooth
sustainable growth. In the Keynesian view, central bankers must have discretionary powers to fulfill their role. Monetarists, under the leadership of
Milton Friedman, believe that discretionary central banking is the problem, not the solution. Friedman believed that growth of the money supply could, and should, be set at a constant rate, to accommodate predictable growth in real GDP. Treynor was one of the developers, along with
William Sharp, of the Capital Asset Pricing Model (CAPM) (for which they won the Nobel Prize in Economics in 1990). was published in 1972. The key insight of the CAPM was that the excess return of an individual stock (over the risk-free rate) is proportional (the so-called beta of the stock) to the excess return of the stock-market. Black viewed the excess return on an individual stock as being linked to the riskiness of that stock, otherwise no-one would buy the stock. He extended this idea into pricing options. Black concluded that discretionary monetary policy could not do the good that Keynesians wanted it to do. He concluded that monetary policy should be passive within an economy. But he also concluded that it could not do the harm monetarists feared it would do. Black said in a letter to Friedman, in January 1972: In 1973, Black, along with Myron Scholes, published the paper 'The Pricing of Options and Corporate Liabilities' in
The Journal of Political Economy. This was his most famous work and included the Black–Scholes equation. In March 1976, Black proposed that human capital and business have "ups and downs that are largely unpredictable [...] because of basic uncertainty about what people will want in the future and about what the economy will be able to produce in the future. If future tastes and technology were known, profits and wages would grow smoothly and surely over time." A boom is a period when technology matches well with demand. A bust is a period of mismatch. This view made Black an early contributor to
real business cycle theory. Economist
Tyler Cowen has argued that Black's work on monetary economics and business cycles can be used to explain the
Great Recession. Black's works on monetary theory, business cycles and options are parts of his vision of a unified framework. He once stated: It has been claimed that the mathematical techniques developed in the option theory can be extended to provide a mathematical analysis of monetary theory and business cycles as well. ==
Business Cycles and Equilibrium ==