This is a short essay on open questions in urban economic theory.

We criticize the theories used to explain the size distribution of cities. They take an empirical fact and work backward to obtain assumptions on primitives. The induced theoretical assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity...

The tomahawk bifurcation is used by Fujita et al. (1999) in a model with two regions to explain the formation of a core-periphery urban pattern from an initial uniform distribution. Baldwin et al. (2003) show that the tomahawk bifurcation disappears when the two regions have an uneven population...

We present a restriction on the domain of individual preferences that is both necessary and sufficient for the existence of a social choice rule that is continuous, anonymous, and respects unanimity. The restriction is that the space of preferences be contractible. Contractibility admits a...

In this paper I describe certain results that were obtained in the UNITAR project based on a model I have specified for studying the relationship between international terms of trade and domestic income distributions of the exporting countries within the South. In particular, I shall concentrate...

We study properties of the solutions to a parametrized constrained optimization problem in Hilbert spaces. A special operator is studied which is of importance in economic theory; sufficient conditions are given for its existence, symmetry, and negative semidefiniteness. The techniques used are...

The long-term trends of urbanization suggest: not only have more cities formed, but the leading metropolises have grown larger, with a number of peripheral subcenters developing over time. Conventional models of urban growth are limited, in that commuting cost and congestion eventually result in...

This paper develops a dynamic model of North-South trade in which environment plays an important role. Our model is based on Chichilnisky North-South model for the macroeconomic interaction between two sectors of the world economy. The latter was introduced in a static context. We introduce...

Oil price behavior has changed dramatically in the last twenty years. These changes can be explained rather simply in terms of the delayed responses of supply and demand to prices, and in terms of changes in the rate of discovery of reserves. This analysis can be used to forecast possible future...

The modern literature on city formation and development, for example the New Economic Geography literature, has studied the agglomeration of agents in size or mass. We investigate agglomeration in sorting or by type of worker, that implies agglomeration in size when worker populations differ by...