We measure the welfare distortions from endogenous quality choice in imperfectly competitive markets. For U.S. cable-television markets between 1997-2006, prices are 33% to 74% higher and qualities 23% to 55% higher than socially optimal. Such quality overprovision contradicts classic results in the literature and our analysis shows that it results from the presence of competition from high-end satellite TV providers: without the competitive pressure from satellite companies, cable TV monopolists would instead engage in quality degradation. For welfare, quality overprovision implies that cable customers would prefer smaller lower quality cable bundles at a lower price, amounting to a twofold increase in consumer surplus for the average consumer.