In addition to using as many sources as we can, our data goes through consistency checks to ensure it's as accurate and reliable as possible. However, there's absolutely no substitute for an international team of movie buffs with an encyclopedic knowledge of trivia and a large assortment of reference works (and we include in this group many of our loyal contributors). Our sources of information include, but are not limited to, on-screen credits, press kits, official bios, autobiographies, and interviews.
Given the sheer volume and the nature of the information we list, occasional mistakes are inevitable and, when spotted/reported, they are promptly verified and fixed. That's why we welcome corrections and submissions.