For doing primary research or finding certain kinds of material, the most efficient way of tracking down information may be to contact an organization which focuses on a specific issue or a person who has published on a topic, works in a government agency, corporation or trade association, or otherwise has access to specialized information.
Statistics and demographic information often play a key role in policy analysis. A vast and complex array of statistical information is available online and in the print collections of libraries. Before attempting to use the more specific and complicated statistical sources, it is good to check one of the statistical compilations published regularly by both the government and commercial publishers. Compilations are especially good for finding a single statistic, e.g., the number of elementary school children in the U.S., the ten most populated cities in the United States, the percentage of the U.S. population which is of Hispanic origin, etc.