The dates when each rating started are:-
Main Ratings = 11/03/2006
Main+Stats Ratings = 11/03/2006
Stats Ratings = 11/03/2006
Tissue Ratings = 29/05/2003
PFR Ratings = 11/10/2002
Trainer Stats Ratings = 11/03/2006
Jockey Stats Ratings = 11/03/2006
Trainer/Jockey Comb Stats Ratings = 11/03/2006
Horse Stats Ratings = 11/03/2006
Pace Ratings = 15/01/2005