Quote Originally Posted by indysteel View Post
Beats me. In all fairness, there is some dispute as to whether certain acronyms, e.g., those with periods, and usages like "the 1980s" should take an apostrophe. I, personally, prefer them without because it seems more consistent with the other rules on apostrophe use. Whichever rule you follow, just be consistent in any given communication.
Most of these types of questions depend on the style book you're referring to.