We characterise endogenous market structures under Bertrand and Cournot competition in a DSGE model. Short-run mark ups vary countercyclically because of the impact of entry on competition. Long-run mark ups are decreasing in the discount factor and in productivity, and increasing in the exit...

I characterise endogenous market structures where leaders have a first-mover advantage and entry is endogenous. Leaders are always more aggressive than the followers, independently from strategic substitutability or complementarity. Under quantity competition, leaders produce more than any...

A new rationale for the persistence of monopolies is based on a precommitment of the incumbent monopolist to invest in R&D. In a patent race, as long as entry is free, the Arrow effect disappears: the incumbent has more incentives to invest than any outsider. Paradoxically, a market with some...