Finding from Asia, Australia, Europe, and North Amercia on secular change in mean height of children, youths, and young adults.

Studies conducted during the past century in Australia, Canada, Japan, Norway and the United States indicate that the magnitude of secular increase in mean height rose with advancing age from childhood to mid-adolescence. Comparisons for a period approximating two-thirds of a century yield average increases in mean height of 12.2 cm for female youths age 12 years, and 12.5 cm for male youths age 14 years; for the same calendar span, the amount of secular increase in mean height declines from mid-adolescence to early adulthood. Comparisons of Belgian females, spanning a period approximating 130 years, yield increases in mean height of 18.1 cm at age 12 years, 11.9 cm at age 16 years, and 3.7 cm in early adulthood. For a period of 90 years, increases obtained on United States White males are 14.8 cm at age 14 years, 8.8 cm at age 17 years, and 5.3 cm in early adulthood. These and other displayed findings show clearly that the search for causes of secular change should take particular account of a phenomenon widespread among human populations, i.e., the phenomenon of childhood and early adolescent growth in body height proceeding at a faster pace in recent decades than about a century ago.