Optimal product variety in radio markets
研究了广播市场中自由进入均衡是否导致过度进入，发现社会规划者会减少50%-60%的电台，且高质电台过多时降低其质量可改善福利。
A vast theoretical literature explores inefficient market structures in free‐entry equilibria, and previous empirical work demonstrated that excessive entry may obtain in local radio markets. We extend that literature by relaxing the assumption that stations are symmetric, allowing for endogenous horizontal and (unobserved) vertical station differentiation. We find that, in most broadcasting formats, a social planner who takes into account the welfare of market participants eliminates 50%–60% of the observed stations. In 80%–94.9% of markets where high‐quality stations are observed, welfare could be unambiguously improved by converting one such station into low‐quality broadcasting, suggesting local overprovision of quality.