Separately, Jimmy Wales reportedly said that 0.7% of Wikipedia's users have made 50% of all Wikipedia edits and 1.8% of users have written more than 72% of all articles, and he was quoted in the New York Times in June as saying “A lot of people think of Wikipedia as being 10 million people, each adding one sentence...But really the vast majority of work is done by this small core community” of about 1,000 Wikipedians.
I believe Aaron Swartz did some statistical analysis on this and found it not to be true .. a small number of editors make the most # of edits, but the content is written by a very large number of editors.