Aside from the equilibrium that Hotelling (1931) displayed, his model of non-renewable resources also contains a continuum of bubble equilibria. In all the equilibria the price of the resource rises at the rate of interest. In a bubble equilibrium, however, the consumption of the resource peters...

Stock-market crashes tend to follow run-ups in prices. These episodes look like bubbles that gradually inflate and then suddenly burst. We show that such bubbles can form in a Zeira-Rob type of model in which demand size is uncertain. Two conditions are sufficient for this to happen: A declining...

The usual explanation for why the producers of a given product use different technologies involves "vintage-capital": A firm understands the frontier technology, but can still prefer an older, less efficient technology in which it has made specific physical and human capital investments. This...

Firm numbers first rise, and then fall as the typical industry evolves. This nonmonotonicity in the number of producers is explained in this paper using a competitive model in which innovation opportunities induce firms to enter, but in which a firm's failure to implement new technology causes...