Plurals of abbreviations - 1990's or 1990s

I think the p's and q's argument is most salient here.  The apostrophe is used for the sake of clarity.  While conventionally used for the possessive, the apostrophe is also used to indicate vernacular omissions and contractions, such as in the cases of "Ol' Dirty ***" or "N'awlins."  This understadning of the usage of apostrophes is important for thinking about the 1990s/1990's problem.  If you were to spell out the actual words 1990 and 1990s/1990's,  you get the words "nineteen ninety" and "nineteen nineties."  The difference between these two words is a "y" and an "ies."    The possessive spelling of 1990's would be "nineteen ninety's," the plural, "nineteen nineties."   The abbreviated representation of the possessive should clearly be 1990's, but what about the plural?  One could argue that the apostrophe in this case stands for the omission of the "ie" in "nineteen nineties" 

Hello fooladder, welcome to the forums.

Obvioulsy, with the possessive, you use the apostrophe.

It was a popular tune sometime back in the early 1990s.

He has 1990's biggest hit record. (Obviously, a possessive.) EDITED for clarity -by this I mean the one year, 1990.

He was the 1990s' most popular enteratiner. (Also possessive.) EDITED for clairty - by this I mean the decade of the 1990s.

I've edited my prior post for clarity. I though it was clear by saying "the 1990s'"  what I meant but apparently not.

I don't think we're disageeing at all here - do you?

I would say 1993, but not 1994. 1994, 1995, and 1996 are the mid-1990s.