I waste a bit of time playing online chess, and I’ve always thought it would be interesting to look at data from these games. In particular, how does my ELO ranking compare to other internet chess players?

This made for a good scraping exercise, and with a bit of coding (python lxml) I scraped some data that could answer my question. Chess.com happens to have over a billion (!) archived games, of which I sampled just over 24,000. The data I scraped were game date, white and black rankings, and game result. Data were analyzed in Matlab.

I first plotted the ranking time-series (Fig 1). Aside from the blip in 2011 (not sure happened there - maybe a big influx of players?), from 2012 on the distribution of rankings looks stable. Since the mean is stable for this period, an average rating of 1293 (SD 299.4) should describe the data pretty well. At first glance, my green line is hovering around the site average. However, is the slight difference noticeable statistically?