Originally Posted by Benhur
A small qualification on the bolded part. It actually happened a total of 14 times (not 13) but two of those instances were in the same year (1977, Vilas and Borg) so it's still 13 separate years. As far as I know that was the only year in the open era when more than one player had percentages above 90 for the year.
The statement in the last sentence is wrong. It hapened also in 1978 (Connors and Borg).