text: USGA Handicap System The first handicap system to be introduced by the USGA was largely the work of Leighton Calkins, who based it on the British "three-score average" system where the handicap was calculated as the average of the best three scores to par in the last year. The key difference was the introduction of a par rating (later known as course rating), which was based on the ability of leading amateur Jerome Travers, to account for variances in the playing difficulty of different courses. After initially allowing clubs to determine their own ratings, at the behest of Calkins the USGA quickly began assigning ratings centrally. Course ratings were rounded to the nearest whole number until 1967, when they started being given to one decimal place.
  In 1947, the number of scores used to calculate handicaps was increased to the best 10 from all scores ever recorded subject to a minimum of 50. However this was not uniformly implemented, with regional associations disagreeing on the total number of rounds to be considered. In 1958, the USGA specified that the best 10 from 25 scores would be used. This was reduced to 10 from 20 in 1967, which remains to this day although a further adjustment was made with the introduction of a "Bonus of Excellence" multiplier to equalize handicaps and give better players a marginal advantage. Originally 85%, the multiplier was changed to 96% after being seen to favor better players too heavily. In 1974, Equitable Stroke Control was adopted in order to eliminate the effect of very high individual hole scores on handicap calculations.