In theory, free entry can lead to social inefficiency. We study the radio industry in a first attempt to quantify this inefficiency. Using cross-sectional data on advertising prices, the number of stations, and radio listening, we estimate the parameters of listeners' decisions and of firms'...

This chapter surveys empirical models of market structure. We pay particular attention to equilibrium models that interpret cross-sectional variation in the number of firms or firm turnover rates. We begin by discussing what economists can in principle learn from models with homogeneous...

In theory, free entry can lead to social inefficiency. When new products are substitutes for existing products, the business stolen from incumbents places a wedge between private and social benefits of entry. The business stealing effect can be offset if entry reduces prices or increases...