Thoroughbred families 1-43 are described by Bruce Lowe's 1895 book, "Breeding Racehorses by the Figure System". The book was formulated using a system of family numbers from mares listed in the General Stud Book. According to Lowe, "The figures are derived from a statistical compilation of the winners of the three great English classic races, Derby, Oaks and St. Leger. The family with the largest number of wins is No. 1, the next No. 2 and so on up to No. 43, and include families whose descendants have not won a classic race."