ImperfectlyInformed, 26/06/2014 02:14:
I'm surprised no one seems to have mentioned that Part I, question 6 of the Form 990 which asks for total volunteers. For year 2011, 85,000 was the number year 2010 has 100,000.
That's just the number of editors taken from WikiStats, as I believe the notes to the actual form 990 explain. You may have missed "the movement" in the subject line; the form 990 is only about WMF properties.
Nemo