British Go Journal No. 13.  April 1971. Page 9.
A Japanese friend kindly gave me the details of the handicapping system used in the Okubo Go Club. The system will be of interest to British players not only far the way in which they adjust the handicaps of their players, but also for the way in which professional players are matched with amateurs.
The strength of professional players is normally judged on the basis of the results of games in competition, on which they spend 10 or 12 hours each. Of course many amateurs cannot give so much time to a single game, and so their strength is on a somewhat different basis.
This means that, although the true strength of top professionals might be about 200 on the index number list on the right, when they play with amateurs their strengths are taken at about 190. Mr. Okubo, 9-dan, who comes to every meeting of the club, is assessed at 180 for the purpose of teaching games.
Each member of the club has a strength assessment in terms of the index numbers, which might either be an exact equivalent of a kyu or dan grade or a halfway position, such as 115 -between 1 and 2 dan.
|Index Number||Equivalent Strength|
|190 ]||] Professional players|
|180 ] }|
|170 }||} Top amateurs|
To calculate the handicap for a particular game, the two index numbers are subtracted, and one stone given for every ten points difference. When an exact division is not possible, Black is given 5 points komi. A special ruling for a difference of only 5 in the index numbers gives White 2.5 points komi, not the 5 komi he gets when the strengths are equal.
It is interesting to compare this system with the old "Europeans system used in Britain until two years ago. The European system gives half a stone more than the Okubo system for every handicap game and thus favours the Black player. A further advantage to Black is in the method of calculating intermediate handicaps, by giving komi.
The Okubo Club play a round of matches lasting about a month, after which the scores of all those members who have played in more than 12 matches are compared. The winner is the one with the highest percentage of wins.
Handicap adjustment is also based on the percentage of wins. Those with percentages over 65 are advanced by 5 points in index number, and those who do worse than 35% are demoted 5 points. For players above strength 150 (5-dan), two consecutive months of over 65% or below 35% are required before a change is made.