The Return to Capital in Ghana

Robert E. Lucas (1990) famously asked, “Why Doesn’t Capital Flow from Rich to Poor Countries?” If there exist aggregate production functions representing approximately the same technology across countries, then the vastly higher output per worker in richer countries implies that capital per worker must be much higher in these countries, and diminishing returns implies a much lower rate of return to capital in rich than in poor countries. The details of the calculation depend, of course, on specific assumptions. However, the magnitudes are sufficiently large that the absence of massive capital flows to the poorest countries is properly seen as a fundamental puzzle. Lucas considers the possibility that capital market imperfections permit the existence of a gap in the returns to capital across countries, but argues that this cannot account for most of the difference implied by his calculation. He, therefore, raises the possibility that there are huge differences in human capital across countries, and externalities associated with these differences imply that returns to physical capital are not so different across countries with even large differences in physical capital per worker. Accordingly, there is no mystery about the lack of physical capital flows. In contrast, Abhijit V. Banerjee and Esther C. Duflo (2005) review a good deal of evidence, mostly from India, showing widely varying and often very high real interest rates. In addition, ∗We are grateful to Marcus Noland for the initial conversation that led to this paper, to Erica Field, Barbara O’Brien and Yuichi Kitamura for valuable comments, and to Hyungi Woo, Tavneet Suri, and Patrick Amihere for research assistance. We thank the Institute for Statistical, Social and Economic Research at the University of Ghana for providing a superb research environment. Financial support was provided by the Pew Charitable Trusts project on The Moral and Social Dimensions of Microeconomic Behavior in Low-Income Communities.