Two by two, inch by inch: Height as an indicator of environmental conditions during childhood and its influence on earnings over the life cycle among twins.

Adult height is a function of genetic predispositions and environmental influences during childhood. Hence, any variation in height among monozygotic twins, who share genetic predispositions, is bound to reflect differences in their environmental exposure. Therefore, a height premium in earnings among monozygotic twins also reflects such exposure. In this study, we analyze the height premium over the life cycle among Swedish twins, 10,000 of whom are monozygotic. The premium is relatively constant over the life cycle, amounting to 5-6% higher earnings per decimeter for men and less for women, suggesting that environmental conditions in childhood and youth affect earnings over most of the adult life course. The premium is larger below median height for men and above median height for young women. The estimates are similar for monozygotic and dizygotic twins, indicating that environmentally and genetically induced height differences are similarly associated with earnings.