Born in Britain, he earned his B.A. in mathematics at King's College, Cambridge in 1969, his M.A. in economics at University of Warwick in 1972, and his Ph.D. in economics at Princeton University in 1974. He then became a fellow at Churchill College, Cambridge and a professor at the London School of Economics. In 1984, he returned to the U.S., where he taught at the Massachusetts Institute of Technology and, since 1993, at Harvard University. He was chairman of the Harvard economics department from 2000 to 2003. He is a Fellow of the American Academy of Arts and Sciences and of the Econometric Society, and a Corresponding Fellow of the British Academy. He has been President of the American Law and Economics Association and Vice-President of the American Economic Association, and has several honorary degrees.
He is an American citizen. He is married to writer Rita B. Goldberg and has two sons and a grandson. He is the son of Philip D'Arcy Hart.
He is an expert on contract theory, theory of the firm, corporate finance, and law and economics. His research centers on the roles that ownership structure and contractual arrangements play in the governance and boundaries of corporations.
Firms, Contracts, and Financial Structure (Oxford University Press, 1995).
"On the Optimality of Equilibrium when the Market Structure is Incomplete",Journal of Economic Theory, December 1975,418-443
"Takeover Bids, the Free-rider problem, and the Theory of the Corporation" (with Sanford J. Grossman), Bell Journal of Economics, Spring 1980,42-64
"An Analysis of the Principal-Agent Problem" (with Sanford J. Grossman), Econometrica (January 1983) 7-46.
"The Market Mechanism as an Incentive Scheme," Bell Journal of Economics, 14 (Autumn 1983) 366-82.
"The Costs and Benefits of Ownership: A Theory of Vertical and Lateral Integration" (with Sanford J. Grossman), Journal of Political Economy, August 1986,691-719.
"One Share-One vote and the Market for Corporate Control" (with Sanford J. Grossman), Journal of Financial Economics, 1988
"Incomplete Contracts and Renegotiation" (with John Hardman Moore), Econometrica 56(4) (July 1988).
"Property Rights and the Nature of the Firm" (with John Hardman Moore), Journal of Political Economy 98(6) (1990).
" A Theory of Debt Based on the Inalienability of Human Capital " with John Hardman Moore, Quarterly Journal of Economics, November 1994,841-879
"The Proper Scope of Government: Theory and an Application to Prisons" (with Andrei Shleifer and Robert W. Vishny), Quarterly Journal of Economics 112(4) (1997) 1126-61.
"Contracts as Reference Points" ( with John Hardman Moore), Quarterly Journal of Economics, February, 2008,1-48.