This disparity in the availability of wholesome food is often cited to explain why the wealthy eat more healthily than the poor. Santa Monica drowns in crisp vegetables, South Los Angeles in crisp bags. It is only logical that residents of the former would eat more fibre and less sugar than residents of the latter. Similar dynamics play out far beyond southern California. Low-income bits of the country are more likely to be “food deserts”, defined by the United States Department of Agriculture as places where one-third of the population lives at least one mile away from the closest supermarket in urban areas and at least ten miles away in rural areas.
But a study by Hunt Allcott of NYU, Rebecca Diamond of Stanford, and Jean-Pierre Dubé of Chicago Booth suggests the disparity in how the rich and poor buy groceries is caused more by demand than supply. Supply gaps are real and glaring, the study concedes. More than half (55%) of ZIP codes with a median income under $25,000 have no supermarkets, compared with 24% of ZIP codes across America as a whole. But, the researchers showed, introducing low-income populations to the same grocery shopping conditions enjoyed by high-income ones reduces nutritional inequality by only 9%. The remaining 91% of the nutritional gap, the academics contend, can be accounted for by differences in demand.