Nutrition gap between rich and poor is growing, but don’t blame food deserts, researchers say
February 13, 2018
For decades, the conventional wisdom has been that people living in food deserts—defined as areas lacking in supermarkets with fresh produce and other nutritious items—have little choice but to buy unhealthy food at drugstores or convenience stores. But the data tell a different story.
Working with Nielsen Datasets shopping data from the University of Chicago Booth School of Business Kilts Center for Marketing, a new study finds that food deserts have no meaningful effect on eating habits.
Exposing low-income households to the same products and prices as those experienced by high-income households reduces nutritional inequality by only 9 percent while the remaining 91 percent of the nutrition gap is driven by difference in what shoppers prefer to buy, according to the National Bureau of Economic Research working paper, “The Geography of Poverty and Nutrition: Food Deserts and Food Choices Across the United States,” by Chicago Booth Professor of Marketing Jean-Pierre Dubé, New York University’s Hung Allcott and Stanford University’s Rebecca Diamond.
“One of the conclusions in our study is that opening a supermarket in a food desert has very little impact on the nutritional composition of households’ shopping baskets,” said Dubé. “People in food deserts shop in supermarkets almost as frequently as people living in higher income neighborhoods. They just travel longer distances to stores.”
The term “food desert” emerged in the 1990s in the United Kingdom as the government’s Social Exclusion Unit task force observed that many low-income households in Britain lacked access to healthy foods. Instead of supermarkets carrying nutritional foods, most poor neighborhoods had only small convenience stores. Government and public policymakers worried that the small stores would lack the economies of scale to carry a broad variety of healthy food at a reasonable price. But there wasn’t much hard evidence to support these concerns.
Two decades later, with the help of Big Data, the researchers Allcott, Diamond, and Dubé decided to design a study that relied on actual grocery purchases to determine why the wealthy tend to eat more healthfully than the poor in the U.S.
The researchers worked with data, from the Nielsen Datasets at the Kilts Center for Marketing, that include grocery purchases by some 60,000 households per year and grocery sales at about 35,000 stores nationwide from 2004 to 2015. Allcott, Diamond, and Dubé also included the locations of 1,914 supermarkets to study the impact that new supermarkets have on healthy eating in food deserts.
They tested whether a household’s geographic location drives food shopping preferences, to understand whether living in a food desert causes residents to purchase less nutritious food. In fact, they find almost no effect of location on purchases. Then they developed an empirical method to estimate the preferences that the households in the panel had for fruits and vegetables, as well as various nutrients such as saturated fat, sugar, and salt.
Among their findings:
Households that earn less than $25,000 a year travel an average of 5 miles each way to buy groceries, clothing, and household hardware, according to the data, while those that live in a food desert travel 7 miles. Even people who are poor, live in a food desert, and don’t have a car, still travel 2 miles.
Households in food-desert zip codes buy almost 90 percent of their groceries from supermarkets.
Wealthier households tend to place a higher value on healthy foods and nutrients, while poorer households tend to value unhealthy ones. High-income households (making more than $70,000 a year) are willing to pay almost double for the daily recommended quantity of vegetables and nearly three times more for daily recommended quantity of fruit, the researchers estimate. By contrast, low-income households (making less than $25,000 a year) are willing to pay more for sugar and saturated fats.
As part of the study, the researchers also developed a Health Index to measure the nutrition content of households’ grocery purchases. The index improved five times more for high-income households than it did for low-income households between 2012 and 2015, compared to 2004 through 2007—indicating the nutritional gap between the rich and the poor is growing.
The authors also find that education and nutrition knowledge are strongly associated with the differences in preferences across income groups. While these findings are not causal, they may suggest that policies aimed at nutrition education may be more effective at closing the nutrition gap than subsidies and grants meant to encourage building more supermarkets and farmers markets in food deserts.
“Food knowledge and education seem to explain a big chunk of the preferences for what people buy when they shop for groceries,” said Dubé. “If you are educated about the long-term benefits of nutrition, it could affect your shopping behavior.”