Taking evolutionary view of markets, Harold Demsetz hypothesized that firms differ persistently in efficiency and that industry concentration results from growth of efficient firms at the expense of inefficient ones. We test the hypothesis with high quality microdata from the US hospital...

Most scholars and antitrust cases have defined hospital service markets as primarily local. But, two recent decisions have greatly expanded geographic markets, incorporating hospitals as far as 100 miles apart. Managed care plans, now important in most markets, were believed to shift patients to...

In an earlier article in The Bell Journal, Tybout argues that even in a zero transaction costs model, bribery to reduce pollution and compensation charges for it result in different total profits, and thus in different long-run behavior. Therefore, the Coase Theorem is refuted for the long-run case.