George P. Stigler, a free-market economist famed for his pioneering studies arguing that government regulations result in inefficiency without protecting consumers, yesterday became the 11th American and the fourth University of Chicago professor to win the Nobel Memorial Award in Economic Science.

A prize worth roughly $157,000 will go to the conservative economist for "his seminal studies of industrial structures, functioning of markets, and causes and effects of public regulations," according to the citation issued in Stockholm by the Swedish Royal Academy of Sciences. Last year's winner was liberal James Tobin of Yale.

Stigler is the Charles R. Walgreen distinguished service professor at Chicago's Graduate School of Business and a past president of the American Economics Association. He told reporters in Chicago that although surprised to have gotten the award, he was "delighted, happy and richer."

Commenting on the current state of the economy, Stigler said high unemployment was the price President Reagan had to pay for reducing inflation from 12.4 percent in 1980. He predicted the jobless rate would drop soon, though slowly.

The award to Stigler, 71, was hailed yesterday by liberal and conservative economists alike.

Undersecretary of State for Economic Affairs Allen Wallis, who has been closely associated with Stigler ever since they both were graduate students at Chicago in 1933, praised the award as one of the best made by the Nobel committee in recent years.

Treasury Undersecretary Beryl Sprinkel, a former colleague of Stigler's at Chicago, said that Stigler is "one of the most witty and relevant economists I ever met." Sprinkel cited the "path-breaking progress" Stigler had made not only in advocating deregulation, but on the "cost of information theory."

Stigler developed what at the time was a new idea: that the cost of information can become an important factor in the decision-making process. For example, a job may be open, but an employer and a suitable prospect may be out of touch, and the cost of disseminating information about the opening may be too high to bring them together.

But Stigler probably had his greatest impact in the 1940s, by developing a theory that government regulation hurt rather than helped consumers.

"I'd call him the 'first deregulator,' " Brookings Institution research director Joseph A. Pechman said yesterday. "I have the highest regard for George Stigler. He's a very prominent economist, probably the leading microeconomist in our midst."

Walter W. Heller, who was chairman of the Council of Economic Advisers in 1962 under President Kennedy, recalled that using "Stiglerian theory" on the costs and benefits of regulation helped him get Kennedy's approval to reduce transportation regulations, overruling the Commerce Department, which had wanted to intensify them.

"Stigler had a tremendous impact on the thinking of all economists on deregulation," Heller said.

Liberal economists, of course, do not entirely agree with a basic theme of Stigler's work, which is that government is not a benevolent force. Stigler's views can be considered an early forerunner of the Reagan philosophy that the best government is that which governs least.

Stigler also has evolved a theory of "public choice," a cynical analysis that suggests that the behavior of government bureaucrats is dictated by an effort to maximize their own self-interest.

In a book entitled "The Citizen and the State," published in 1975, Stigler endorsed as "irresistible" economist Friedrich von Hayek's argument that "comprehensive political control of economic life" will reduce personal liberty to an unacceptable minimum.

Stigler undertook to prove that there have been specific "invasions of personal freedom" through government regulation. Two of his best-known studies in this area relate to the regulation of electric utilities and the stock market. In the first, he charged that the real beneficiaries were not the average homeowner, but large industrial and commercial users of electricity. In the second, he contended that Securities and Exchange Commission regulations provide "a clear instance of where the gains are not worth the costs." Stigler believes that the SEC, like other government regulatory bodies, imposes large costs on the public by suppressing competition.

"I have neither inclination nor evidence to deny the regulatory process occasional triumphs," Stigler wrote. "The delay in introducing thalidomide in the United States presumably was a splendid success. But we must base public policy . . . upon the regular, average performance of the policy. If the policies which delayed thalidomide would delay a new penicillin at least as long -- as seems highly probable -- we must reckon this in the costs of the program."

Among his most influential writings are two books, "The Theory of Price, Capital and Rates of Return in Manufacturing Industries," a widely used textbook, and "Intellectuals and the Market Place."