Oil market share dynamics: A Markov chain analysis of consumer and producer adjustments

We develop an “optimal market share rule” model of cartel behavior which when applied to the OPEC cartel appears capable of explaining its stability and responses to changed market events. In particular, by attaching importance to market shares based approximately on costs, OPEC members can by maintaining optimal shares deter deviant member attempts to break cartel rules. After a thorough discussion of the theory, the model is tested empirically using a Markov probability model. The estimated Markov transition matrix is further decomposed into what Theil has called the exchange matrix and the mean passage matrix. Dynamic adjustment processes in the market are revealed by the latter while an emerging pattern of OPEC member surveillance of consumers is revealed by the former which facilitates cartel stability. Inspection of these matrixes further suggests that after the formation of OPEC there is evidence of less potential for producer conflict while there appears more evidence for consumer conflict. While these results must be tentative in view of the fact that they have been estimated using a simplified two consumer — two producer model and limited data, it is argued that the results are highly suggestive and the approach in this study can be extended to cover all producer and consumers, and can be integrated into a complete model of the world oil market.