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...

Policy rules that are consistent with inflation targeting are examined in a small macroeconomic model of the US economy. We compare the properties and outcomes of explicit instrument rules' as well as targeting rules.' The latter, which imply implicit instrument rules, may be closer to actual...