摘要：Whether or not the marginal product of capital (MPK) differs across countries is
a question that keeps coming up in discussions of comparative economic
development and patterns of capital flows. We use easily accessible
macroeconomic data to shed light on this issue, and find that MPKs are
remarkably similar across countries. Hence, there is no prima facie support for
the view that international credit frictions play a major role in preventing
capital flows from rich to poor countries. Lower capital ratios in these
countries are instead attributable to lower endowments of complementary factors
and lower efficiency, as well as to lower prices of output goods relative to
capital. We also show that properly accounting for the share of income accruing
to reproducible capital is critical to reach these conclusions. One implication
of our findings is that increased aid flows to developing countries will not
significantly increase these countries' incomes.
