The following data covers several major sourcebooks from 2009-2010. All data is based on analysis of a randomly-selected set of 7-8 briefs, except where noted. Columns are organized in roughly decreasing order of credibility. (Note that “Other People” is an inclusive category with widely varying credibility.)
Disclaimer: Opinions vary on what constitutes a credible source; what is represented here is the opinion of the authors. You are, of course, welcome to hold your own opinions and analyse the data however you want, but don't complain to the authors that they got it all wrong. Thank you.
Major Orgs – Big, respected organizations like the World Health Organization or the National Academy of Sciences PhDs – Academic sources - not necessarily limited to actual PhDs (individuals with PhDs, professors, and law and science journals) Major News – Big, respected newspapers like the New York Times Think Tanks – Policy analysis institutions like the Cato Institute or the Heritage Foundation SIGs & Orgs – Special Interest Groups or advocacy organizations, like the Natural Resources Defense Council or WWF Other News – Miscellaneous minor (mostly online) news services, like Greenwire Other People – Miscellaneous other people, like the CEO of Exxon Mobil or the President of Brazil (credentials vary)
Sources are placed in the highest applicable category – for example, someone with a PhD writing for the Heritage Foundation would be listed under "PhDs", and someone with a think tank affiliation writing for a minor news source will be listed under “Think Tanks.” Opinion pieces and editorials are evaluated by the author, not by the newspaper it appeared in.