I have posted the summary results from the Japanese pro database before. Here is a little more detail.
To repeat for ease of comparison:
|Percentage versus komi||Black||White|
The size of the komi therefore appears to have a clear effect: at first glance 1 point komi is not too far off 1 percentage point. However, there is a curious phenomenon to account for. In the period 1986-95 (i.e. roughly half the period of 5.5 komi alone) White improved his ratio slightly (Black won 16,146 games = 52.7%, White 14,510 ), which implies it was worse in the first half of this period. This is attributed by the Nihon Kiin to the beneficial effect (for White) of nirensei by White, popular in that period, and the relative failure of the sanrensei for Black (I have already posted these figures).
Another oddity is that Black does even better in 7-game title matches. In these he has a winning ratio of 54.2%. Possibly the very best players can exploit Black's inherent advantage a little bit more? Tentative proof of this is a comparison of the winning ratios for the top players, viz.
|As Black||As White|
|Top 15 pros||68.1%||61.6%|
Two players in this list (O Rissei and Ryu Shikun) actually have a higher winning ratio with White, but in both cases they are well above 70% with either colour. There are several more oddities lower down the lists. E.g. Enda Hideki has a 64.6% winning ratio with White but only 51.5% with Black - the biggest discrepancy this way round. There are lots of players who have big winning ratios with Black and small ones with White. One big gap is Kanashima Tadashi 9d (Black 67.3%, White 49.0%). All these figures are based only on komi games for players who have played at least 200 games.
-- John Fairbairn