Originally Posted by krosero
So the bias in the ATP stats, when they're wrong, is toward big servers like Sampras, Becker, Ivanisevic.
Not just their total points won, but their service percentages and success on first and second serve, are going to appear higher than they actually were.
Actually success on second serve is going to skew low in the ATP stats, if double-faults are being counted twice. And that would often affect the big servers, or anyone who had a bad day double-faulting.
Doing a quick review of the boxscores above from the print media, they do give players greater success on second serve than the ATP does, but less success on first serve.