Aaron Director, who died Saturday at his home in Los Altos Hills, Calif., is credited with combining the fields of law and economics, possibly the most influential legal doctrine of the 20th century. He insisted that economic statistics be applied to the law in both conception and execution.

A fierce proponent of free markets and open societies, it was Director who was responsible for getting the University of Chicago to publish the American edition of Friedrich von Hayek’s “The Road to Serfdom.”

Although Director himself published little, his influence was manifest on his students and colleagues, including Robert Bork, Richard Posner, and Frank Easterbrook. George Stigler, a colleague of Director’s at Chicago and himself a Nobel laureate, said, “Most of Aaron’s articles have been published under the names of his colleagues.”

Ronald Coase, another Chicago colleague and Nobelist, said, “In all, he was a very civilized man. But he did not like any argument that was not solid, because his own arguments were always very solid.”

Director emigrated from Russia to America as a teenager, and settled in Portland, Ore., where his father worked as a peddler with a horse and wagon and later opened a store. Recruited to attend Yale, Director as a young man had leftist and even radical leanings. Together with fellow Yalie and Oregonian Mark Rothko, he produced the “Yale Saturday Evening Pest,” a weekly publication that assailed careerism. The Pest’s manifesto declared, “…if vested interests or respectable people do not put an end to us, nought shall escape us.” Sinclair Lewis sent them an encouraging note.

After college, Director worked as a migrant laborer, textile worker, and coal miner before hopping a cattle boat to England. From there he visited France and Czechoslovakia to study adult education of workers. He returned to Oregon, where he was named head of the Portland Labor College. In 1927, he undertook graduate studies in economics at the University of Chicago, where he studied price theory and unemployment, and abandoned any socialist impulses entirely.

According to Mr. Coase, his thinking was transformed by Jacob Viner. “It is easy to understand why a solid course by this great teacher and great economist would have swept away like chaff in a windstorm the nebulous idealism and Socialist views of Director’s Yale days,” Mr. Coase wrote.

Director published his only book, “Unemployment,” in 1932, although he co-authored two others; his journal articles and reviews were more influential, including one of “The Road to Serfdom.”

After having his book published in Britain, Hayek had been unable to find an American publisher. Even Director could prevail on the University of Chicago Press to publish only 2,000 copies. The book ended up selling over 200,000 and became one of the milestones in the development of modern conservatism.

Hayek, in turn, helped prevail on the University of Chicago to establish an institute of political economy, with Director at its head, in 1946. Director taught at the law school.

Recalling Director’s classroom conduct, Mr. Bork recalled studying law under Edward Levi. Levi would teach traditional legal theory for four days a week, and Director would lecture on the same topics on the fifth.

“One of the pleasures of [the antitrust course] was to watch Ed agonizing as these cases that he had always believed in were systematically turned into incoherent statements,” Mr. Bork said in an oral history of the Chicago program.

In 1958, Director founded the Journal of Law & Economics, which became the touchstone for emerging doctrines. Among these, as he saw them, were that “there is room neither for subsidies to individual economic activities or for price fixing of particular products,” and he argued for the removal of tariffs and tax biases in favor of corporations, and the reform of patent law to favor innovation. He also said, “Monopolistic determination of wages is in no sense different from monopolistic fixing of enterprises. If they are not to be trusted with governing industry, neither are unions.” And “I know that there is widespread belief that the proper solution is responsible or statesmanlike behavior on the part of those who hold too much power. I regret to say that I am skeptical and find more wisdom in Adam Smith’s observation: ‘I have never known much good done by those who affected to trade for the public good.'”

Director retired in 1965, and built a home in Los Altos Hills, where he lived near his sister, Rose, who had married the economist Milton Friedman while both were in graduate school at Chicago. It was a measure of Director’s own conservatism that he referred to Friedman affectionately as “My radical brother-in-law.”

For recreation, Director favored woodworking, and made intricate jigsaw puzzles that he presented to the children of friends. Director never married.

In retirement, Director worked at the Stanford University Law School, and at one point returned to Chicago to teach an antitrust course with Mr. Posner. While Director’s influence in some ways peaked during the Reagan years, with their emphasis on deregulation and the transformation of antitrust law, it continues somewhat more subtly throughout the practice and theory of the law. According to one study, by 1993 articles using economic analysis were cited in major American law journals in greater numbers than those using any other legal methodology.

Aaron Director

Born in 1901 in Charterisk, Russia (now in Ukraine); died Sept. 11 at Los Altos Hills, Calif.; survived by his sister, Rose.