The early ranking systems were "averaging" systems; total points divided by tournaments played. Usually, the only tweaking that went on was with the minimum divisor or the points allotment. In the early days, there were a lot of decimals, and your #1 player would have an average like 15.xxxxxxxxx. They later boosted the points to make the numbers easier to comprehend for the average fan. (And to make them look better.) The tour went to a "rolling 52" system in 1997, whereby the points were just added up. The complaint was that it dramatically favored those who played more. So results were capped, first at 18, then 17 tourneys. There were still complaints of the system favoring "quantity over quality", but when you consider that 1 tournament win gives you more points than 4 quarterfinal finishes, that complaint seemed groundless.
Interestingly, one of the complaints voiced last year was that the system didn't allot enough points for slam wins; "only" twice that of a Tier I. Those critics called for a return to systems similar to the past. Ironically, under one of the old systems cited as desirable, slams were only awarded 75% more points than a Tier II.