How to Identify Food Deserts:
Measuring Physical and Economic Access
to Supermarkets in King County, WA
Junfeng Jiao, Anne Vernez-Moudon Dr. es Sc.,
Jeffrey Ulmer, Phillip Hurvitz PhD., Andrew Drewnowski.
American Journal of Public Health. 2012, 102(10):e32-9. PMID: 22897554
This study introduced new concepts and measures to identify food deserts.
Physical and economic access to supermarkets were estimated for five low-income groups in Seattle-King County. Physical access was measured using GIS to delineate service areas around each supermarket based on a 10-minute travel duration by four modes: walking, bicycling, riding transit, or driving. Economic access was assessed by stratifying supermarkets into low-, medium-, and high-cost types. Combining income and access criteria generated multiple ways to estimate food deserts.
The five low-income group definitions yielded total vulnerable populations ranging from 4 to 33% of the County’s population. Almost all of the vulnerable populations lived within a 10-minute drive or bus ride of a low- or medium-cost supermarket. Yet a high of only 34% of the vulnerable populations had the option of walking to any supermarket, and a low of 3% did so to a low-cost supermarket.
The criteria used to define low-income status and access to supermarkets greatly affect estimates of populations living in food deserts. Measures of access to food must include travel duration and mode, and supermarket food costs.
Research supported by R01DK076608-04 (A. Drewnowski PI)