Why do people have ambiguity aversion, preferring, a gamble with a 50% chance of success to one whose expected probability of success is 50% but where that 50% is an unbiased estimate? The answer modelled here, in the spirit of the career concerns literature, is learning: a risk-averse person...

Consider a Bertrand model in which each firm may be inactive with a known probability, so the number of active firms is uncertain. This activity level can be endogenized in any of several ways-- as whether to incur a fixed cost of activity, as output choice, or as quality choice. Our model has a...

Consider a Bertrand model in which each firm may be inactive with aknown probability, so the number of active firms is uncertain. Thissimple model has a mixed-strategy equilibrium in which industryprofits are positive and decline with the number of firms, the samefeatures which make the Cournot...