How reliable is the information in comic-book Statements of Ownership?
As opposed to validity, reliability is more of a judgment about the measure itself: How well is it reporting what it says it is? The reliability of the Statements in the 1970s and onward is generally pretty good, given the comparisons I’ve been able to make with archival info from the publishers themselves. Looking at them across an entire year or range of years for a publisher, it’s pretty easy to see when a figure is outside what we’d expect. Most tend to square up with other known sales figures fairly well. Errors, when they happen, generally tend to be computational in nature, involving transposition of numbers. But there are much bigger ones, resulting in complete data loss. Marvel once accidentally ran the previous year’s form in Iron Man, for example. And in a handful of cases, the forms simply didn’t appear at all for whatever reason — as was the case with Amazing Spider-Man in 1979.
