Prior to 2008, the ATP used two different systems to rank men's tennis players. Between 1994 and 1999, players were ranked on the basis of their best 14 results in the calendar year. Between 2000 and 2008, players were ranked on the four Grand Slams plus 14 other competitions.
Between 1994 and 1998, the ATP ranked players solely on their best 14 results in competition. However, in 1999 a rule change was brought in to reflect the importance of the competition won. This meant that winning a Grand Slam or a Super 9 event was worth more ranking points than winning a Champ Series or World Series event.
Between 2000 and 2008, further changes to the ranking system prioritized the Grand Slam events. During this period, results from the four Grand Slams and nine Masters Series events counted towards the ranking regardless of results. Players could also use five optional results from Champ Series, World Series, Challengers and Futures events. If a player didn't qualify for a Grand Slam or Masters Series event, he could choose an additional optional event to count towards ranking points. Points were awarded on a sliding scale depending on the importance of the event and the final position within the event.