From Supersizing supercenters? The impact of Walmart Supercenters on body mass index and obesity, by Charles Courtemanche and Art Carden, Journal of Urban Economics 69 (2011) 165–181
Researchers have linked the rise in obesity to technological progress reducing the opportunity cost of food consumption and increasing the opportunity cost of physical activity. We examine this hypothesis in the context of Walmart Supercenters, whose advancements in retail logistics have translated to sub- stantial reductions in the prices of food and other consumer goods. Using data from the Behavioral Risk Factor Surveillance System matched with Walmart Supercenter entry dates and locations, we examine the effects of Supercenters on body mass index (BMI) and obesity. We account for the endogeneity of Walmart Supercenter locations with an instrumental variables approach that exploits the unique geo- graphical pattern of Supercenter expansion around Walmart’s headquarters in Bentonville, Arkansas. An additional Supercenter per 100,000 residents increases average BMI by 0.24 units and the obesity rate by 2.3% points. These results imply that the proliferation of Walmart Supercenters explains 10.5% of the rise in obesity since the late 1980s, but the resulting increase in medical expenditures offsets only a small portion of consumers’ savings from shopping at Supercenters.