The Evolution of Value Orientation of American Antitrust Law Guo Yue(77) The Antitrust Law of the United States did not initially take economic efficiency as its principal value orientation when the Sherman Act was adopted. In view of historical facts, the initial value orientation of antitrust law was ambiguous or, in other words, the law tried to pursue multiple goals. The values of populism, which originated in the traditional social and political ideology of America, later dominated the development of antitrust law. It was only after the 1970s when the United States was facing a different economic situation at home and broad that economic efficiency became the main value orientation of antitrust law. The Chicago School that bitterly criticized the antitrust policy carried out before also contributed a lot to that change.