Think tanks form a knowledge-based network that engages with new ideas, promotes their dissemination, and contributes to the shaping of political debate and public policy. Although think tanks are nonprofit and nonpartisan, they are not necessarily non-ideological. The decentralized nature of the American political system, along with weak party discipline and the nation's philanthropic culture, has led to the proliferation of over two thousand think tanks across the entire range of ideological perspectives.

The first half of the twentieth century saw the creation of some of the country's most important think tanks: Carnegie Endowment for International Peace (1910); Hoover Institution on War, Revolution, and Peace (1919); Council on Foreign Relations (1921); Brookings Institution (1927); and American Enterprise Institute (AEI, 1943). These early think tanks were focused primarily on producing the highest quality academic research. In essence, they functioned as universities without students. Their goal was not to influence public policy directly...