This is a survey of the economic principles that underlie antitrust law and how those principles relate to competition policy. We address four core subject areas: market power, collusion, mergers between competitors, and monopolization. In each area, we select the most relevant portions of...

In this paper we develop a monopolistic competition model where firms exercise their market power across multiple products. Even with CES preferences, markups are endogenous. Firms choose their optimal product scope by balancing the net profits from a new variety against the costs of...

Patent protection spurs innovation by raising the rewards for research, but it usually results in less desirable allocations after the innovation has been discovered. In effect, patents reward inventors with inefficient monopoly power. However, previous analysis of intellectual property has...

This study provides a new theoretical result that a decline in the long-term interest rate can trigger a stronger investment response by market leaders relative to market followers, thereby leading to more concentrated markets, higher profits, and lower aggregate productivity growth. This...

Market power arises in the case where a seller is aware that raising output will depress price. In the profit-maximizing equilibrium with market power, price exceeds marginal cost. The Lerner index---the ratio of price less marginal cost to the price---is a widely accepted measure of market...

This paper estimates the extent to which market power is a source of production misallocation. Productive inefficiency occurs through more production being allocated to higher-cost units of production, and less production to lower-cost production units, conditional on a fixed aggregate quantity....