John Maurice Clark (born 30 November 1884 in Northampton, Massachusetts; died 27 June 1963 in West Haven, Connecticut) was an American economist whose work combined the rigor of traditional economic analysis with an "institutionalist" attitude.
Clark studied at Amherst College, graduating in 1905, and received his Ph.D. from Columbia University in 1910. He was an Instructor at Colorado College (1908-1910) and at Amherst College (1910-1915). In 1915 he joined the faculty of political economy at the University of Chicago. He accept a professorship at Columbia in 1926, where he remained until he retired in 1957.
Throughout his career Clark was concerned with the dynamics of a market economy, or Competition as a Dynamic Process, the title of his last work. In Studies in the Economics of Overhead Costs, Clark developed his theory of the acceleration principle, that investment demand can fluctuate widely when consumer demand fluctuates; in this he anticipated key Keynesian theories of investment and business cycles.  Clark is considered one of the founders of the theory of workable competition, neither pure competition nor pure monopoly, a neglected Marshallian insight.
With his theory of X-efficiency, Harvey Leibenstein demonstrated that the measurability of the market price of products in a monopoly is very difficult to obtain.
John Maurice Clark was the son of John Bates Clark, and shared his view of the importance of ethical and policy issues. Both father and son worked jointly on the revision of John Bates Clark's The Control of Trusts (1914), work continued by John Maurice in Social Control of Business (1926, revised in 1939).
Clark was President of the American Economic Association in 1935, and was awarded the Francis A. Walker Medal in 1952.
History of economic thought
|Early Modern||Scholasticism · Mercantilism · Physiocrats|
|Modern||Classical Economics · English historical school · German historical school · Socialist economics · Neoclassical economics · Lausanne school ·Institutional economics|
|20th-century||Stockholm school · Keynesian economics · Austrian school · Chicago school|