Growth, Capital Shares, and a New Perspective on Production Functions Preliminary — Comments appreciated Charles I. Jones* Department of Economics, U.C. Berkeley and NBER E-mail:
[email protected] http://elsa.berkeley.edu/~chad June 12, 2003 – Version 1.0 Standard growth theory implies that steady-state growth in the presence of exponential declines in the prices of computers and other capital equipment re- quires a Cobb-Douglas production function. Conventional wisdom holds that capital shares are relatively constant, so that the Cobb-Douglas approach might be a good way to model growth. Unfortunately, this conventional wisdom is misguided. Capital shares exhibit substantial trends and fluctuations in many countries and in many industries. Taken together, these facts represent a puzzle for growth theory. This paper resolves the puzzle by (a) presenting a produc- tion function that exhibits a short-run elasticity of substitution between capital and labor that is less than one and a long-run elasticity that is equal to one, and (b) providing microfoundations for why the production function might take the Cobb-Douglas form in the long run. Key Words: Growth, Leontief, Pareto, Capital Share, Equipment Prices, Steady State JEL Classification: O40, E10 *I am grateful to Pete Klenow, Sam Kortum, and Alwyn Young for helpful conversations during the genesis of this paper and to seminar participants at Arizona State University, the Chicago GSB, Stanford, and U.C. Berkeley for comments on an earlier draft. This research is supported by NSF grant SES-0242000. 1 2 CHARLES I. JONES This paper is motivated by a collection of stylized facts that, when taken together, are puzzling from the standpoint of modern growth theory.