What was the economic impact in England of the 14th-century plague known as the Black Death? It's not clear, according to a 45-page study reprinted by the Federal Trade Commission at a cost of $115.

What's not clear to Sen. Thomas F. Eagleton (D-Mo.) is why the FTC cares.

"How in the world can a study of economic conditions during the British plague of 1348-51 have any possible relevance to the work of today's FTC?" Eagleton asked this week in a letter to FTC Chairman James C. Miller III.

"Minimal as the costs for producing this work may have been, it sends a very ugly message to the taxpayers of this country, especially at a time when the FTC is cutting back in areas like antitust enforcement . . . for which there is a vital need," Eagleton wrote.

Agency spokesman Merrie Spaeth said that the study is useful to the agency because of its economic modeling techniques. "It was well within the framework of industrial economic analyses," which the FTC occasionally reprints and makes available to researchers, she said.

"I know the title makes us look stupid," Spaeth said. "If it were titled 'Mass Dislocations Resulting From Government Regulatory Policy,' no one would care."

The study was done by FTC economist Judith Gelman in 1979, while she was studying at the Massachusetts Institute of Technology.