Why is Health Related to Socioeconomic Status?

There are striking disparities in morbidity and mortality by socioeconomic status (SES) within the United States. I examine pregnancy and health at birth to investigate possible mechanisms linking SES and health. I find that a limited set of maternal health habits during pregnancy, particularly smoking habits, can explain about half (one third) of the correlation between SES and low birth weight among white (black) mothers. I show evidence on three hypotheses to explain why health habits vary by SES. First, differences in knowledge by SES create only modest differences in health behaviors by SES, explaining about 10 percent of differential smoking by education. Second, women respond to common knowledge differentially by SES, so that knowledge and its use combined explain up to one third of differential smoking by education. Third, the most important determinants of differential health behavior are 'third variables,' or variables that can simultaneously determine health habits and SES. Finally, I show evidence that network effects at the family level exacerbate differences in behavior regardless of the source.