Historically, urban growth required enough development to grow and transport significant agricultural surpluses or a government effective enough to build an empire. But there has been an explosion of poor mega-cities over the last thirty years. A simple urban model illustrates that in closed...

This paper develops a general theory of aggregation in inefficient economies. We provide non-parametric formulas for aggregating microeconomic shocks in economies with distortions such as taxes, markups, frictions to resource reallocation, financial frictions, and nominal rigidities. We allow...

The paper develops a simple stochastic new open economy macroeconomic model based on sticky nominal wages. Explicit solution of the wage-setting problem under uncertainty allows one to analyze the effects of the monetary regime on welfare, expected output, and the expected terms of trade....