"It's a pretty concentrated market already," he said.

But the company may drop out of civilian aircraft manufacturing, leaving one competitor fewer in an already highly concentrated market.

In such a concentrated market, a manufacturer could not afford to make a single strategic mistake, he said.

Telecommunications networks, they can argue, are naturally concentrated markets because of high investment costs, and wireless prices have declined after past mergers.

Like any concentrated market, the threat is that the hospital giants will price-gouge or, worse, succumb to lazy, second-rate care.

Most operate in concentrated markets with few players, making it easy to coordinate pricing.

The biggest problem faced by Intervest is that it is trying to break into a concentrated market, in which size is very important.

Very few alcohol producers or distributors survived prohibition, creating a concentrated market ripe for abuses.

This would guarantee a large enough pool of potential test subjects in concentrated markets to allow studies to proceed.

This feature of concentrated markets is the subject of the paper by Rees in this issue.