This appendix provides additional information on the methodology used in calculating the number of think tanks active in American policy making by the mid-1990s, as well as details about the characteristics, perceptions, and visibility of think tanks.

Counting Think Tanks

My estimate of the number of think tanks operating in American politics in the 1990s, as reported in Chapter 1, is based on an examination of a variety of sources and background materials. I draw on references from directories, books, and scholarly articles about think tanks as well as newspaper and magazine clippings to arrive at a count of 306 organizations. The single most comprehensive source of think tank listings, and the one upon which I depend most, is Hellebust's Think Tank Directory. In sorting through Hellebust's entries, I excluded from my database organizations that are not independent or not oriented toward affecting public policy debates. After I narrowed Hellebust's list of organizations, 302 institutions qualified as think tanks according to my definition. I included an additional four think tanks in the database based on references made in a variety of other sources. The four organizations added were Campaign for America's Future, a liberal/progressive think tank founded in 1996; Institute for Energy Research, a conservative, Texas-based think tank founded in 1989; Institute for Gay and Lesbian Strategic Studies, a scholarly, liberal-oriented research organization started in 1994; and, the German Marshall Fund, a research and grantmaking institution founded in 1972. The first three may have been overlooked by Hellebust because they are new and relatively small.