Optimal timing of defections from price-setting cartels in volatile markets

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.