As of today there's a pretty neat new privilege, site analytics, that lets you see a couple of neat graphs. I was playing around with it and noticed something odd: a very strong spike in downvotes in May 2013. Here it is in its glory: the weekly total of downvotes since the site's graduation in February 2011:
It contains 972 downvotes for that week, with current totals around 650. It's concentrated on the 6th and 7th, with 233 and 282 votes, and with 143 and 147 on the 8th and 9th.
I dug around the data explorer and didn't find anything, which makes me suspect the offending posts have been deleted (and therefore makes me hesitate to ask this question) but I'm still curious. Can anyone pinpoint the origin of this thing?
The localized nature of the spike suggests that it's one or two related posts driving it (in which case they totalled 3x as many downvotes as the rest of the site's average) or e.g. a sockpuppet racket, in which case the data should not really include them.
(That said, I might as well make this useful and urge others with the privilege to go look, and to encourage those in the 10-25k range to keep going. Also, kudos to joshphysics for referring to the site more traffic than MO and just under half the traffic from reddit!)