Question source: How sportsmanlike are our users?

Data sources: June 6, 2011 NDA dump; February 6, 2012 NDA dump

The results here are only for Stack Overflow.

How many sportsmanlike votes have been cast?

June, 2011      Answer votes:     9,687,945
                Competing votes:    363,454 (3.75%)

February, 2012  Answer votes:    14,072,290
                Competing votes:    468,421 (3.33%)

• The Sportsmanship badge was introduced near the end of October, 2010 -- it's possible that people were still becoming aware of the badge by June, 2011 and were going out of their way to vote for competing answers, and now it's basically leveled off. I didn't do a time-series analysis to find out. It would be interesting to run the analysis again in 6 months.
• The number of competing votes is relatively small compared to the total number of votes. That's somewhat expected because generally you don't submit an answer if your viewpoint has already been articulated by someone else.

Which users cast sportsmanlike votes?

• For the calculations, when a competing vote was cast, the user's approximate reputation at the time of the vote was used.
• I would caution about doing a trend analysis between the different ranges -- the ranges aren't even, so I'm not sure they're directly comparable (i.e., the "spike" in the 1000-1999 range is due to the grouping). For that, a continuous graph would be better instead of grouping by key reputation ranges.
• It's pretty clear that 10k+ reputation users do a significant amount of sportsmanlike voting because that group accounts for only ~0.25% of registered users, yet ~20% of sportsmanlike votes.
• Even though overall competing answer voting went down, the 10k+ reputation range went up significantly (+14.7%).

When do sportsmanlike votes occur relative to a competing answer?

June, 2011:      24.96 days
February, 2012:  28.75 days

• I suspect these results reflect a huge amount of skew, where (a) now people submit sportsmanlike votes closer to the time, and (b) sportsmanlike votes are submitted against aging/very old answers (which could be over 1,200 days old at this point).
• People definitely revisit old answers to submit sportsmanlike votes... which is, ironically, somewhat unsportsmanlike (badge-motivation in action). (For comparison, I remember doing another analysis that showed most activity in an average question occurred within the first 7 days of a question being asked.)

If you'd like to have a look at all statistics I collected for this question, you can download the Excel spreadsheet here.