Measuring the Incentive to Collude: The Vitamin Cartels, 1990–99
研究了1990年代维生素卡特尔的稳定性，用重复博弈方法量化并购的“协调效应”，发现维生素C卡特尔在1995年崩溃时合谋激励为负，而长期存在的维生素A、E和β-胡萝卜素卡特尔在1999年被起诉前激励始终为正。
Abstract Do mergers help or hinder collusion? This article studies the stability of the vitamin cartels in the 1990s and presents a repeated-games approach to quantify “coordinated effects” of a merger. We use data and direct evidence from American courts and European agencies to show the collusive incentive of the short-lived vitamin C cartel was likely to be negative when it actually collapsed in 1995, whereas the incentives of the long-lived cartels (vitamins A and E, and beta carotene) were unambiguously positive until the prosecution in 1999. Simulations suggest some mergers could have prolonged the vitamin C cartel, but others could have further destabilized it, because both the direction and magnitude of coordinated effects depend not only on the number of firms but also on their cost asymmetry.