The initiative for the creation of the Official World Golf Ranking came from the Championship Committee of the Royal and Ancient Golf Club of St Andrews, which found in the 1980s that its system of issuing invitations to The Open Championship on a tour by tour basis was omitting an increasing number of top players because more of them were dividing their time between tours, and from preeminent sports agent Mark McCormack, who was the first chairman of the International Advisory Committee which oversees the rankings. The system used to calculate the rankings was developed from McCormack's World Golf Rankings, which were published in his World of Professional Golf Annual from 1968 to 1985, although these were purely unofficial and not used for any wider purpose (such as inviting players to major tournaments).