Policy File Index This link opens in a new windowPolicy File Index is a unique resource for U.S. public policy research in that it grants users access to timely, updated information from over 350 public policy think tanks, nongovernmental organizations, research institutes, university centers, advocacy groups, and other entities. Over 75 public policy topics are covered, from foreign policy to domestic policy. The majority of Policy File Index records link directly to the full-text report, paper, document, or other source.