Differences in the Local Food Environment Are Not the Main Cause of Nutritional Inequality
Diet is an important driver of obesity and other health outcomes. However, many studies show evidence of nutritional inequality, where low-income households tend to eat less healthfully than high-income households. Policymakers and others point to the fact that low-income neighborhoods often suffer from a lack of supermarkets and other large grocery stores that offer a wide array of healthy foods. In a 2019 study, a researcher from USDA’s Economic Research Service and academic researchers explored why high-income households tend to eat more healthfully than low-income ones in the United States. The researchers tried to determine if nutritional inequality between income levels is mainly caused by the local food environment—such as having a nearby supermarket, prices at local food stores, and local attitudes towards health—or by other factors that drive differences in demand for healthy groceries between high-income and low-income households.
The researchers first showed that the entry of a new supermarket into a neighborhood did not significantly improve the healthfulness of residents’ grocery purchases, as measured by a slightly modified version of USDA’s Healthy Eating Index. They estimated that access to a nearby supermarket explained no more than 1.5 percent of the difference in the healthfulness of grocery purchases between high- and low-income households (high income was defined as above the 75th percentile in household income; low income was defined as below the 25th percentile).
The researchers also found that households that move between counties and zip codes did not significantly change the healthfulness of their grocery purchases. From this finding, the researchers estimate that “place effects” of the local food environment, such as the eating habits of friends and neighbors, and concerns related to healthy eating, contributed no more than 3 percent of the difference in the healthfulness of grocery purchases between high- and low-income households.
The researchers continued their analysis by applying a model of consumer demand for groceries to actual retail purchase data to estimate households’ demand for healthier groceries. The results show that high-income households have stronger demand for healthy dietary components, such as whole fruit and whole grains, and a stronger aversion to unhealthy components such as added sugar and sodium. The study linked these differences in demand to potential differences in education levels and nutritional knowledge. Using these estimated preferences, the analysis infers that if the high- and low-income groups were given equal access to the same food items and faced the same prices, nutritional inequality in grocery purchases would only reduce by 10 percent. The researchers concluded that 90 percent of nutritional inequality is driven by differences in demand for healthy groceries between high-income and low-income households.
Allcott, H., Diamond, R., Dubé, J. P., Handbury, J., Rahkovsky, I., & Schnell, M. Food deserts and the causes of nutritional inequality, The Quarterly Journal of Economics, 134(4), 1793-1844. doi:10.1093/qje/qjz015, January 2019