The Goat Debate

[FredX]

Maybe a trigger was the AO moving to January..until then, it wasn't considered equal to the other majors so people didn't count majors as if it was the thing...so if we want a cutoff date, maybe that is it?

The thing is, those other majors also weren't exactly equal to each other. Players were missing French Open for some other competitions (Team Tennis?). Laver after his CYGS in 1969 clearly stopped prioritizing slams and his 1970 season shows this. He was #3 in weighted ranking (which is heavily influenced by Slams performance), but still #1 in Opponents' Index. Therefore it is extremely hard to quantify the importance of each Slam back then.

Right, there's no one point where they became important, they just gradually grew in importance, and not all at the same time. Theoretically at least (would be tons of work!) you could decide an individual slam's importance by the number of top players who appeared in it. I'm sure the 1969 Wimbledon would rank higher than the 1975 Australian Open etc.

[ponchi101]

Wimbledon and the US Open are secure in their position of the most important tournaments. That is for sure.
But some smaller tournaments were more "important" than the other two current majors simply because they had some advantages. I would wage some money that Queens ranked higher than the Aussie, by the metric you propose, simply because it was also in London and it was a preamble to Wimbledon. So a lot of players would show up for it, while a lot of high ranked players would skip the Aussie simply because of the logistics.
And maybe the Italian Open ranked as high as RG simply because they were similar: glamorous city, long history, roughly similar prize money in the early days of pro tennis.
As you say, the Slams became more important when the federations (and the AELTC) realized how much money there was there to be made. And made them more important with the exorbitant prize money and huge number of points. We all know that making the semis of a slam not only makes you more money than most other tournament, it gives you more points than anything other than a 1000, and basically guarantees you automatic entry in the next four slams, meaning again more money.