Short history of the 'Masters'
The 'Masters' tournaments exist only since 1990. The Grand Prix series of tournaments, conceived in 1969 by Jack Kramer, are the most likely equivalent earlier on.
However, another separate circuit -the World Championships Tennis (WCT)- existed already since 1967. Both circuits merged only in 1985, so we'll try and publish asap more details on the WCT.
In 1970 the Grand Prix circuit had 27 tournaments, including 3 Grand Slams (the Australian Open being part of the WCT circuit). From that year on, the year's Top 8 players over the Grand Prix tournaments qualified for the 'Masters Grand Prix' year-end finals, the unofficial worldchampionships for tennis, and soon nick-named 'the Masters'.
Since 1970, not only the rules for the TMC changed frequently, but also the number of participants (from 6 to 8) and even its name :
- Masters Grand Prix from 1970 to 1989,
- ATP World Tour Championships from 1990 to 1999,
- Tennis Masters Cup from 2000 to 2008,
- ATP World Tour Finals from 2009 on.
The early Grand Prix tournaments were mostly played by the independent players. Contract players had their own rival circuit (WCT) with its own 'worldchampionships' and entered the Grand Prix tournaments only if their contractors allowed them to (mostly when no WCT tournaments were held at the same time). 1990 was the last year a WCT tournament was organised, the last WCT finals were held in 1989.
The 70's & 80's top-players seem to have been more attracted to the TMC than to the Australian Open. The TMC might have been the 4th most important tournament to Borg and McEnroe, after Roland Garros, Wimbledon & the US Open. Played shortly after the US Open, the Masters were the season's climax, after which many players preferred to skip the Australian Open (in those days still scheduled at the end of the year).
We tried to find a way to compensate this discrepancy with today's Australian Open 'standing' by comparing the Australian Open versus the TMC.