We consider a two-player advertising race subject to momentum. Momentum is modelled as a complementarity between current and past campaign spending in a way that is reminiscent of models of addiction and habit formation: the more effective a player's past spending has been, the more effective...

We study contests in which the prize depends on the number of participants, and show that equilibrium effort can be increasing, decreasing, or non-monotonic in the number of participants. This contrasts with the standard result for contests with fixed prizes in which effort is decreasing in the...