Fig. 2A–B.

Relative skeletal age (skeletal age – chronological age) versus chronological age is presented by birth cohort in (A) boys and (B) girls. Greater relative skeletal age indicates earlier maturation. The lines estimate the average relative skeletal age at a given chronological age for boys and girls. The early cohort (solid line) has relative skeletal age near zero at all ages (note that this cohort represents the individuals used to develop the Fels method). The recent cohort (dashed line) has relative skeletal age greater than zero, indicating earlier skeletal maturation.