I’ve always said that the smaller the footnote or the simpler the question, the more time it will take to find the footnote’s supporting document or a citable document to answer the question.
We were recently asked how many states have three-strikes laws. Now, you would think this would be straightforward, but it’s not. There are many studies, many articles, many commentators, and many, many assumptions.
We find reports from a few years ago, tons of stuff from California on their recent legislation, some excellent research out of Hawaii on their 2009 legislative action to repeal their 3-strikes law, but nothing that can be used as a reliable current citation for all 50 states. I have charts from 2000, writers and journalists who say there were 23 states in 2004, 26 states in 2004 (Wikipedia, unfootnoted), and a fairly reliable study from 2006 that says 25 states. But nothing actually or even relatively official or authoritative (e.g. government or think-tank or nonprofit) from 2007 forward.