Note that in 2001, While Venus and Serena were NOT ranked #1 or #2, They actually took home MORE prize money from tournaments, by WINNING or placing well in the Tourneys that had the BIGGIST purses. Ericsson, Indian Wells, Wimbledon, Canadian Open, US Open, Sannex Championships.
I believe they were #1 and #2 last year in prize money, dispite playing a VERY light schedule.
I say they ARE dominating... When they please.