The principle of WFA was developed by Admiral Rous, a handicapper with the English Jockey Club.
This weight varies depending on the horse's age, its sex, the race distance and the month of the year.
WFA is a method of trying to equal out the physical progress which the average thoroughbred racehorse makes as it matures.
It is also necessary to take into account the race distance because stamina comes with maturity, and younger horses are at a greater disadvantage the farther they have to run.
If no allowance was made, a mature older horse would always beat a younger one.