Wish I could be of more help Elegos.
The rankings were so mysterious in the old days that no one could really keep track of them. We only found out decades later that for two brief weeks in 1976 Evonne Goolagong was #1!
Part of the trouble was that points were not only were given for prize money, but also the strength of the field. Thus a $100,000 event with Chris Evert in 1978 might feature more points than a $120,000 event without Evert.
I am aware of the complexities of the WTA ranking system in the 1970s. However, there was a reform in 1984, when the rankings became better predictable.
This is what I gathered of this new WTA computer ranking system from the spring of 1984.
- In 1983 the WTA hired James Broder as Director of Management Information Systems early in the year and post Wimbledon he had come up with a new ranking formula that replaced the system in place since 1975. Although complex, this was extremely thorough, accurate and reflected the quality of more recent wins of a player.
- More importantly because he assigned values to tournaments based on prize money ahead of time, as opposed to deciding this after based on who entered, it was now possible for players and Tour staff to compute ahead of time, with the aid of a calculator, what their ranking would be. Previously this was impossible.
- The new averaging system (which maintained 12 as the minimum divisor) had three main elements:
1) the round points assigned based on the amount of prize money offered at an event,
2) bonus (quality) points were awarded based on the current ranking of the player who you had a victory over (given for wins over Top 200 players),
3) plus a new element, whereby after points earned after 26 weeks decreased by 50% and retained that value until dropping off completely after the 53rd week they were earned.
- This formula was overwhelmingly approved at the end of the year and put into operation at the beginning of the 1984-85 Virginia Slims World Championship Series on March 6.
I found a report about the WTA computer rankings in 1986:
- The WTA divides tournaments into 10 categories, but considers the type of event more heavily than the prize money offered. Category 1 events are $10,000 satellite tournaments at which the winner earns one point. At the high end of the scale are the Grand Slam events - category 10 tournaments - which award 300 round points to the winner. All the Grand Slams carry the same amount of points for the women, whether they offer $5000,000 or $5,000,000 in prize money.
- "Our point structure is designed to reflect the strength of a tournament more," says James Broder, the WTA's director of Management Information Systems. "Our primary events, like the 'Virginia Slims Of' tournaments, get the strongest fields since the WTA is committed to produce a number of top players for these events. What we want to do is create a distinction between primary and nonprimary events. So a $250,000 nonprimary event like the Queens Grand Prix, for instance, has the same point structure as a $150,000 primary event like the Virgina Slims of Dallas."
- In addition to round points, a win over any of the top 300 women gives the victor various amounts of bonus points.
- The WTA encourages its top two drawing cards, Navratilova and Chris Evert Lloyd, to play in lesser-money events with a rule that stipulates they are guaranteed their averages upon winning.
- The elimination of the "diminishing return" ranking system. That system discounted a player's points by 50% six months after they'd come on the computer. It encouraged a player to go out and play to keep her average high. But the system was scrapped because many of the top players, spearheaded by Navratilova, felt it was especially injurious to them.
Beginning with 1987 the official WTA site has usually the round points a player has earned, but there is no info about the bonus points. And there is no info about the round points before 1987.
I heard Marian Ciulpan plans to reconstruct the historical WTA rankings as well, just as he did with the ATP rankings. So maybe in a few years we will have more info.