This paper, an extension of the Presidential Address to the International Economic Association, evaluates alternative strands of macro-economics in terms of the three basic questions posed by deep downturns: What is the source of large perturbations? How can we explain the magnitude of...

A significant amount of the increase in the wealth income ratio in recent decades is due to an increase in the value of land. We present a series of models that explain why land prices may have increased. These models help us understand the increase in both the wealth income ratio and wealth...

A second extension analyzes the effects of land. We ask whether land holding displaces the holding of capital, resulting in workers being worse off. A tax on land, while reducing the value of land, leaves unchanged the capital-labor ratio, output per capita, and wages. But the tax reduces the...

Among the key results are: (i) The magnitude of wealth inequality does not, in general depend on the difference between the rate of interest (r) and the rate of growth (g); the former is itself an endogenous variable that needs to be explained. In the standard generalization of the Solow model,...

Explaining why the concepts of "capital" and "wealth" are distinct, we show that appropriately defined aggregates for wealth may be (and in the case of some countries appear to be) moving in opposite directions

This paper analyzes equilibrium, dynamics, and optimal decisions on the factor bias of innovation in a model of induced innovation. In a model with full employment, we show that (a) if the elasticity of substitution is always less than or greater than unity, there is a unique steady state...

It concludes by constructing a simple model in which knowledge flows slowly across national borders but moves easily within borders. We show there is a leadership-followership equilibrium, in which some countries are leaders, others are followers. Contrary to Solow's analysis, there need not be...

The pace of innovation is related both to the level of investment in innovation and the pool of knowledge from which innovators can draw. Both of these are endogenous: Investments in innovations are affected by the pool of knowledge and the ability of firms to appropriate the returns to their...