In this article, we study the optimal regulation of a dominant firm when an unregulated firm actively competes. Generally, the existence of an active rival imposes new and binding constraints on regulatory problems. We characterize optimal policies both when demands are known (complete...

Firms compete with prices and qualities in markets where consumers have heterogeneous preferences and cost characteristics. Consumers demand two goods, which can be supplied jointly or separately by firms. We consider two strategy regimes for firms: uniform price-quality pairs, and screening...