Cartels are inherently instable. Each cartelist is best off if it breaks the cartel, while the remaining firms remain loyal. If firms interact only once, if products are homogenous, if firms compete in price, and if marginal cost is constant, theory even predicts that strategic interaction...

Both in the US and in Europe, antitrust authorities prohibit merger not only if the merged entity, in and of itself, is no longer sufficiently controlled by competition. The authorities also intervene if, post merger, the market structure has changed such that "tacit collusion" or "coordinated...