By the end of the twentieth century, think tanks were ubiquitous in American policy making. From fewer than 70 in 1969, the number of think tanks had expanded to more than 300 by the late 1990s. Whereas in the 1960s, only the Center for Strategic and International Studies had a name that began with “center,” by the late 1990s, 28 think tanks used that word in their name, ranging from the Center for Defense Information to the Center for Defense of Free Enterprise, from the Center for Equal Opportunity to the Center for New Black Leadership, from the Center for Democracy and Technology to the Center for Military Readiness.

As their numbers grew, think tanks came to vary substantially in size and specialties. Many new think tanks identified with political ideologies – broadly conservative, liberal, or centrist. Many relied on aggressive, marketing-oriented strategies to promote their products and points of view. Think tank staff often became active and visible participants in deeply partisan and divisive political debates.

Yet in their growing numbers and increased activism, there is little indication that the overall impact of think tanks as sources of expertise is expanding. Think tank influence does not appear to have grown in proportion to the growth in think tank numbers. The role of think tanks in the policy process often has become one focused more on providing skewed commentary than neutral analysis.