Raymond Rees, Ulrich Woitek, University of Munich, and
N.V. Long, Montreal

The diverging trends in physical stature and in real income of the free population of the ante-bellum United States, white and black, has both puzzled and fascinated economic historians. One would hardly have expected adult men to become 2 cm. shorter within a generation prior to the Civil War when per capita income was growing at the respectable rate of 1.4% per annum (Weiss, 1992). The Afro-American experience is of particular interest in this context, since there is accumulating evidence to suggest that, in contrast to the trend for the free population, the terminal heights of the male birth cohorts of slaves of the 1830s and 1840s were increasing, while those of females and boys tended either to remain unchanged or to diminish only slightly (Steckel 1995a; Komlos and Coclanis, 1997). Inasmuch s as this pattern has been found in two separate samples of slaves, one based on Georgia convicts and the other on slaves shipped in interregional trade from the Upper to the Lower South, it is unlikely to be a statistical artifact.
In this paper, we argue that this anomaly can be explained as an outcome of rational wealth-maximizing behavior by slave owners. While the declining heights of the free population could be seen as a result of reduced food intake in response to the rising relative prices of food, slave-owners would base their decisions about how well to feed slaves on the movement of cotton prices relative to food prices, given the effects of feeding on the productivity of slave labor. A slave is viewed as a capital asset, the productivity of which would decline if nutritional standards were lowered. Slave prices reflect the capitalized value of the net returns to slaves, and the fact that during the ante-bellum decade slave prices increased by 64% relative to food prices lends support to the idea that increasing slave heights reflect higher nutritional standards, which in turn are a response to the returns to higher slave productivity.