In the Sabinas and Poznan populations, BMI shows only modest sexual difference, yet Progreso has many girls much heavier than expected. During maturation, Poznan girls are a little thinner than the boys, whereas in Sabinas the opposite occurs and recurs in Ram�n's (1976) sample of Mexico City elite students. Progreso students, especially the girls, are more stocky than the others. Ram�n found that some Mexico City girls reached 22 BMI at 15 and boys at 17 years.