Originally Posted by jmnk
Those rankings are most likely based on a variation of ELO ranking where the strength of the opponent and the result are taken into consideration to come up with some kind of match value. Read up on Canada Rogers ranking - they are likely similar.
The algorithm we use is actually an iterative algorithm based on the old STAR system that the USTA used back when they calculated head-to-head rankings.
STAR is very complicated - I'm not going to go into it more than to point out the FAQ entry above that another poster references.