Physics and Slavery: The Relative Cost of Calories for Slave Infants and Their Mothers

摘要

In Time On The Cross Robert Fogel and Stanley Engerman use as the rate of slave expropriation the percent of income produced by slaves that was not spent on their maintenance. The authors measure both income and maintenance in terms of expected present value evaluated at birth. They calculate the value of maintenance costs for slaves of different ages from the cost of per capita slave maintenance by using 'Atwater's weights.' In their review of Time On The Cross, Paul David and Peter Temin criticize this approach. They argue that the figure derived for slave maintenance cost is too high, because the food costs per calorie for children were lower than for adults. They maintain that there is 'some substantial basis for thinking that calories are provided in relatively inexpensive forms during childhood. Breast-feeding is an exemplary practice in this regard.' Since the methods employed by Fogel and Engerman give more weight to children than to adults, their value for maintenance costs would be biased upward. Therefore their rate of expropriation would be too low. The example of breast-feeding is the only support that David and Temin give for their contention that the cost per calorie was less for children than for adults.