What Non P writes, is correct. The Tennis Base is the largest and best data base for the whole tennis history, with thousands of newly found data integrated . Maybe still new findings of matches and tournaments of the past emerge (thanks to careful and solid researchers like No Mercy), so the data provided can change a little bit over time.
The problem for the ATP rankings since 1973 is, that the ATP changed their whole ranking system several times. In the 1970s, it was a average percentage system of average points won per events played, not an addition point race system like today, with 2000, 1000, 500 and 250 categories. It could (and in fact will be) very well, that many ATP rankings of the 1970s and 1980s would change dramatically, if you use the point race system of today. See the 1975, 1977 or 1978 ATP rankings for example. Tennis Base is using a modern point system for the whole tennis history.
The poster Slasher has reconstructed the weekly ATP rankings from 1968-1973 on the basis of the then intact ATP system on a weekly basis. Its on a different forum, so i cannot cite it here. For Rod Laver for instance, he has a weekly Nr. 1 ranking of 187, from spring 1968, the birth of open tennis, to 1972. This covers only the open era period of the players careers.
