Guidelines For the Merger Thicket

The Justice Department issues new antitrust regulations

Will this merger tend to create a monopoly or will it further competition? That simple question can often lead to a bewilderingly complex discussion among economists and antitrust lawyers about what exactly constitutes a market. Whether the product in question is shoes or steel, it is first necessary to size up the market before deciding whether or not a merger or acquisition endangers competition.

Last week the Justice Department took an important step toward clearing up the confusion. In the first major revision of antitrust guidelines since 1968, Attorney General William French Smith released a...