We model cartel defection in markets with stochastic demand fluctuations as an investment timing problem. We show that (i) the optimal timing of cartel defection is pro-cyclical, suggesting higher probability of competitive pricing during booms; and (ii) the defection trigger is a positive function of demand variability, and larger than its deterministic demand counterpart, implying that market volatility facilitates collusion. The first result is consistent with the counter-cyclical pricing prediction originally due to Rotemberg and Saloner (1986), but not dependant on lack of persistence in demand fluctuations. The analysis reveals insights on implications of co-variation between volatility and demand shocks.
Working Paper 003
2006, Economic Modelling, 23(5), 792-804