There has been considerable consolidation in the hospital industry in recent years. Over
900 deals occurred from 1994-2000, and many local markets, even in large urban areas, have
been reduced to monopolies, duopolies, or triopolies. This surge in consolidation has led to
concern about competition in local markets for hospital services. We examine the effect of
market structure on competition in local hospital markets - specifically, does the hardness
of competition increase with the number of firms? We extend the entry model developed by
Bresnahan and Reiss to make use of quantity information, and apply it to data on the U.S.
hospital industry. In the hospital markets we examine, entry leads to a quick convergence
to competitive conduct. Entry reduces variable profits and increases quantity. Most of the
effects of entry come from having a second and a third firm enter the market. The fourth
entrant has little estimated effect. The use of quantity information allows us to infer that
entry is consumer-surplus-increasing.