Think tanks are nonprofit policy research organizations that provide analysis and expertise to influence policymakers. From the 1970s their number exploded in the U.S. and their proliferation represented a hope that lawmaking might become better informed and more effective as a result of these expert contributions. Instead, as this book documents, the known ideologies of many, especially the newer, think tanks currently contribute to an environment in which they differ little from advocacy organizations, promoting points of view and preordained policy prescriptions. As a result, they fail to achieve desired influence and undermine their credibility.