The U.S. State Department Central Files are the definitive source of American diplomatic reporting on political, military, social, and economic developments throughout the world in the 20th century. Concentrating exclusively on those Central Files that have not been microfilmed by the National Archives or other publishers, UPA's microfilm editions of the Central Files nonetheless dwarf the State Department's very selective volumes of the Foreign Relations of the United States (FRUS). Containing less than one percent of the material in the Central Files, FRUS focuses on U.S. relations with individual countries but does not include coverage of many of the key topics to which the majority of the original files are devoted. Each part of the Central Files contains a wide range of materials from U.S. diplomats in foreign countries: special reports on political and military affairs; studies and statistics on socioeconomic matters; interviews and minutes of meetings with foreign government officials; court proceedings and other legal documents; full texts of important letters, instructions, and cables sent and received by U.S. diplomatic personnel; voluminous reports and translations from foreign journals and newspapers; and countless translations of high-level foreign government documents. The State Department continued to track the evolution of apartheid from 1955 to 1959. In 1956, the National Party passed the Industrial Conciliation Act, which regulated certain jobs such as operating elevators and driving trucks by race and denied the benefits of collective barganing to blacks. In 1958 as in 1953, U.S. observers saw the National Party increase its majority in parliament. In 1959, the government abolished white-held seats representing blacks in the parliament and in provincial legistlative bodies on the grounds that such representation was made redundant by the increased strength of black local governments in the reserves. The Central Filse also record action taken by opposition organizations.