Maybe I'm not understanding what you are trying to do with this graph. If you took into account everyone in your league, the stats should equal out to 50% overall. 1 person wins and 1 person loses each match. I agree that it would be very interesting to see winning percentages for specific handicap vs specific handicap(how does a 4 fair against a 5). This sounds like a lot of work for someone to do though. I do appreciate you taking the time to make your graph, I'm just not sure what it shows.
Andy
Andy