Thanks for this nice information. Who else is in the list?
Sampras is one behind Federer with 7. The American notched up over 80% match wins from 1993 to 1998 and he was very close in 1992, winning 79% of matches played.
Lendl would have had 10 in a row from 1980 to 1989 but he finished with 79% of matches won in 1984 so his best is 6. Nadal also has 6 consecutive seasons with over 80% of matches won (2005 onwards) and is likely to keep it up in the coming years.
I'm not sure about Jimmy Connors or John McEnroe, although I am pretty sure they do not match Roger in achieving the feat for 8 seasons in a row.