Quiz Question: What was the year that had the most ATP male number 1's?
large scroll down......
1999 was the year that had the most players ranked number 1 during some part of the year. There were five number 1's that year. Pete Sampras, Carlos Moyà, Andre Agassi, Yevgeny Kafelnikov and Patrick Rafter.
(I have just added this to the Wikipedia ranking site - thought it might be interesting).