That poor people have a less healthy diet than rich people is not in doubt. That poor people have worse health because they have less healthy diets is also not in doubt. That poor people have less access to healthy food than rich people is, again, not in doubt. This series of observations has led to a predominant narrative: that the poor are denied the healthy foods that they would choose, where it only that they had equitable access to healthy options.
This does not follow, any more than the argument that low access to contraception is causative of high birth-rates. It is quite feasible that low demand is the cause of both low access and the corresponding outcomes, both in the case of the pill and low access to healthy food.
Allcott and colleagues addressed this issue with respect to diet and health. They examined the possibility that observed differences in supply of healthy foods are a response to differences in the demand for those foods in different neighbourhoods. The authors examined this through a rich array of data sets, one of which covered nearly half of all US grocery purchases. They were able to examine how people of different socioeconomic group behave when supermarkets are established in new locations, or when people move into, or out of, food ‘deserts’. Effectively they treat these geographic changes as instrumental variables.
When they examined the effect of entry of a new supermarket in a given locality, they find that local supermarket entry does not materially increase healthy eating. Then they examined the converse – movement of a household to an environment where more healthy food is available. Again, behaviour does not converge towards the general eating pattern in the new location.
Could this be because the supermarkets charge more for healthy products in poor neighbourhoods than they do in rich neighbourhoods? The authors examined this possibility and were able to exclude it. What they found is that poorer households are willing to pay much less than wealthier households for healthy food. As a result they are provided with less healthy food.
The results are broadly consistent with studies on education and food preferences. Food deserts exist, but they are not the result of supply-side failure. Rather they reflect the role of culture and tastes in the United States, as they have been shown to do in so many other places. The effects observed in the study did not change over many years. Policy initiatives that simplistically target food deserts are thus unlikely to succeed.
— Richard Lilford, CLAHRC WM Director
- Allcott H, Diamond R, Dubé J-P. The Geography of Poverty and Nutrition: Food Deserts and Food Choices Across the United States. NBER Working Paper No. 24094. 2018.