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Multimarket contact effect on collusion through diversification


  • Hwa Ryung Lee


This study establishes the potential positive relationship between multimarket contact (MMC) and sustainable collusive profits under demand fluctuations. In particular, I focus on the correlation structure between demand shocks over multiple markets and show how it can lead to a positive link between collusive profit and MMC. Simple theoretical models show that, regardless of whether demand shocks are observable or not, MMC may improve collusive profits through diversification of demand shocks over overlapping markets. If firms meet in multiple markets and link those markets in the sense that deviation in any market will trigger simultaneous retaliations in every market, then a cheating firm will optimally deviate in every market. Demand fluctuation that a firm is facing in its markets in total will be reduced as the number of markets increases, unless demand shocks are perfectly and positively correlated between the markets. The reduction of demand fluctuations can boost collusion (1) by reducing the temptation to deviate in the period of high demand when demand shocks are observable and (2) by reducing the frequency of costly punishment on the equilibrium path when demand shock is unobservable. The conclusion in the case of observable demand shock provides us with a new testable implication that price competition will be muted by MMC in periods of high demand.

Suggested Citation

  • Hwa Ryung Lee, 2010. "Multimarket contact effect on collusion through diversification," IEW - Working Papers 501, Institute for Empirical Research in Economics - University of Zurich.
  • Handle: RePEc:zur:iewwpx:501

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    1. Fudenberg, Drew & Levine, David I & Maskin, Eric, 1994. "The Folk Theorem with Imperfect Public Information," Econometrica, Econometric Society, vol. 62(5), pages 997-1039, September.
    2. Matsushima, Hitoshi, 2001. "Multimarket Contact, Imperfect Monitoring, and Implicit Collusion," Journal of Economic Theory, Elsevier, vol. 98(1), pages 158-178, May.
    3. Spagnolo, Giancarlo, 1999. "On Interdependent Supergames: Multimarket Contact, Concavity, and Collusion," Journal of Economic Theory, Elsevier, vol. 89(1), pages 127-139, November.
    4. Green, Edward J & Porter, Robert H, 1984. "Noncooperative Collusion under Imperfect Price Information," Econometrica, Econometric Society, vol. 52(1), pages 87-100, January.
    5. Hughes, Kirsty & Oughton, Christine, 1993. "Diversification, Multi-market Contact and Profitability," Economica, London School of Economics and Political Science, vol. 60(238), pages 203-224, May.
    6. Thomas, Charles J. & Willig, Robert D., 2006. "The risk of contagion from multimarket contact," International Journal of Industrial Organization, Elsevier, vol. 24(6), pages 1157-1184, November.
    7. Margaret C. Levenstein & Valerie Y. Suslow, 2002. "What Determines Cartel Success?," UMASS Amherst Economics Working Papers 2002-01, University of Massachusetts Amherst, Department of Economics.
    8. Switgard Feuerstein, 2005. "Collusion in Industrial Economics—A Survey," Journal of Industry, Competition and Trade, Springer, vol. 5(3), pages 163-198, December.
    9. William N. Evans & Ioannis N. Kessides, 1994. "Living by the "Golden Rule": Multimarket Contact in the U. S. Airline Industry," The Quarterly Journal of Economics, Oxford University Press, vol. 109(2), pages 341-366.
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