The ideological position a person or party takes may be explained in terms of social and economic policy. The ideological positions a person assumes on social and economic policy issues may differ in their position on the political spectrum. Milton Friedman was left-of-center on social issues but right-of-center on fiscal matters and is often identified as "libertarian." Several ideological demographics may be identified in addition to or as subgroups of liberals and conservatives, with nearly every possible ideology being found in the general population. In the United States, the major parties overlap heavily in terms of ideology, with the Democrats more to the left and the Republicans more to the right. Social scientists Theodore Caplow "et al." argue that "the Democratic party, nationally, moved from left-center toward the center in the 1940s and 1950s, then moved further toward the right-center in the 1970s and 1980s". Small parties such as the Libertarian Party play a minor role in American politics.