The Transition to Post-Industrial BMI Values in the United States
The trend in the BMI values of the United States population has not been estimated accurately because time series data are unavailable and because the focus has been on calculating period effects. This chapter attempts to estimate long-run trends and the rate of change of BMI values by birth cohorts, stratified by gender and ethnicity, beginning with the mid-nineteenth century. The transition to post-industrial BMI values began in earnest after the First World War and, after slowing down during the Great Depression, accelerated with the spread of television viewing. While period effects provide an upper bound when the weight change occurred, birth cohort effects provide a lower bound. In the absence of longitudinal data, both effects need to be considered. Hence, the evidence leads to the hypothesis that transition to post-industrial weights probably started considerably earlier than hitherto asserted.