World Real Interest Rates

We think of the expected real interest rate for ten OECD countries (our counterpart of the world economy) as determined by the equation of aggregate investment demand to aggregate desired saving. Stock-market returns isolate shifts to investment demand, and changes in oil prices, monetary growth, and fiscal variables isolate shifts to desired saving. We estimated the reduced form for CDP-weighted world averages of the expected short-term real interest rate and the investment ratio over the period 1959-88. The estimates reveal significant effects in the predicted direction for world stock returns, oil prices, and world monetary growth, but fiscal variables turned out to be unimportant. Structural estimation implies that an increase by one percentage point in the expected real interest rate raises the desired saving rate by onethird of a percentage point. Simulations of the model indicated that fluctuations in world stock returns and oil prices explain a good deal of the time series for the world average of expected real interest rates; specifically, why the rates were low in 1974-79 and high in 1981-86. The model also explains the fall in real rates in 1987-88 and the subsequent upturn in 1989. The fitted relation forecasts an increase in the world average of real interest rates in 1990 to a value, 5.6 %, that is nearly a full percentage point above the highest value attained in the entire prior sample, 1958-89. We estimated systems of equations for individual countries' expected real interest rates and investment ratios. One finding is that each country's expected real interest rate depends primarily on world factors, rather than own-country factors, thereby suggesting a good deal of integration of world capital and goods markets.

Quality Improvements in Models of Growth

Technological progress takes the form of improvements in quality of an array of intermediate inputs to production. In an equilibrium that is standard in the literature, all research is carried out by outsiders, and success means that the outsider replaces the incumbent as the industry leader. The equilibrium research intensity involves three considerations: leading-edge goods are priced above the competitive level, innovators value the extraction of monopoly rents from predecessors, and innovators regard their successes as temporary. We show that, if industry leaders have lower costs of research, then the leaders will do all the research in equilibrium. However, if the cost advantage is not too large, then the equilibrium research intensity and growth rate depend on the existence of the competitive fringe and take on the same values as in the standard solution. We discuss the departures from Pareto optimality and analyze the determination of the economy's rate of return and growth rate.

Convergence

A key economic issue is whether poor countries or regions tend to grow faster than rich ones: are there automatic forces that lead to convergence over time in the levels of per capita income and product? We use the neoclassical growth model as a framework to study convergence across the 48 contiguous U.S. states. We exploit data on personal income since 1840 and on gross state product since 1963. The U.S. states provide clear evidence of convergence, but the findings can be reconciled quantitatively with the neoclassical model only if diminishing returns to capital set in very slowly. The results for per capita gross domestic product from a broad sample of countries are similar if we hold constant a set of variables that proxy for differences in steady-state characteristics.Economic

Technological Diffusion, Convergence, and Growth

We construct a model that combines elements of endogenous growth with the convergence implications of the neoclassical growth model. In the long run, the world growth rate is driven by discoveries in the technologically leading economies. Followers converge toward the leaders because copying is cheaper than innovation over some range. A tendency for copying costs to increase reduces followers' growth rate and thereby generates a pattern of conditional convergence. We discuss how countries are selected to be technological leaders, and we assess welfare implications. Poorly defined intellectual property rights imply that leaders have insufficient incentive to invent and followers have excessive incentive to copy.