About the Atlas

Overview

Limited access to supermarkets, supercenters, grocery stores, or other sources of healthy and affordable food may make it harder for some Americans to eat a healthy diet.  Expanding the availability of nutritious and affordable food by developing and equipping grocery stores, small retailers, corner markets and farmers’ markets in communities with limited access is an important part of the Healthy Food Financing Initiative.

There are many ways to define which areas are considered "food deserts" and many ways to measure food store access for individuals and for neighborhoods. Most measures and definitions take into account at least some of the following indicators of access:

  • Accessibility to sources of healthy food, as measured by distance to a store or by the number of stores in an area.
  • Individual-level resources that may affect accessibility, such as family income or vehicle availability.
  • Neighborhood-level indicators of resources, such as the average income of the neighborhood and the availability of public transportation.  

In the Food Access Research Atlas, several options are available to describe food access along these dimensions.

ERS's Food Access Research Atlas was built using Environmental Systems Research Inc. (ESRI) ArcGIS Server technology. The background topographic and satellite maps, as well as the address locator service, were also provided by ESRI.

Measures of food access

The Food Access Research Atlas maps food access indicators for census tracts using ½-mile and 1-mile demarcations to the nearest supermarket for urban areas, 10-mile and 20-mile demarcations to the nearest supermarket for rural areas, and vehicle availability for all tracts. Users of the Atlas can view census tracts by food access indicators using these different measures to see how the map changes as the distance demarcation or inclusion of vehicle access changes. The map includes updated estimates using 2015 data and allows users to compare these new estimates with those from 2010.

New information and mapping features

Several new indicators and mapping features have been added to the mapping tool which provide users with additional information:

  • Because census tract boundaries have not changed, users are now able to compare 2015 estimates of access with 2010 estimates. 
  • Poverty plays a primary role in defining food deserts, and users can now look up the poverty rate and median family income for tracts.
  • Estimates of access by race and Hispanic ethnicity are now available for users to view and download.
  • Users can now look up estimates of the number and share of housing units receiving benefits from the Supplemental Nutrition Assistance Program (SNAP) that are more than ½ mile, 1, 10, or 20 miles from the nearest store.

Data availability and updates

Estimates in the Atlas for 2015 are based on a 2015 list of supermarkets, the 2010 Decennial Census, and the 2010-14 American Community Survey (ACS). The estimates for 2010 are based on a 2010 list of supermarkets, the 2010 Decennial Census, and the 2006-10 ACS.

Changes in methods between 2010 and 2015

Methods used to estimate low-income and low-access census tracts in 2015 are largely the same as methods used in previous estimates. There are, however, a few notable differences.

Spatial analysis, string matching, and manual review methods were used to merge the SNAP and TDLinx data sets to construct a combined store directory. This combined directory comprises all the supercenters, supermarkets, and large grocery stores from each data set, with duplicates eliminated as much as possible to avoid double counting. The matching process identified SNAP and TDLinx stores that were within a 1/3-mile radius of one another or within the same zip code. An automated string matching algorithm was used to identify exact or similar store name-address matches which were then manually verified. Supermarkets from either the SNAP or TDLinx systems without a match in the other system were included in the final combined directory.

For vehicle access, tract-level 2010-2014 estimates of the share of housing units without vehicles is multiplied by the 2010 count of housing units to obtain an estimate of the number of households without vehicles. The share of individuals below 200 percent of poverty is multiplied by the 2010 population to obtain an estimate of the number of people with income at or below 200 percent of poverty. These numbers and shares are then allocated down to the ½-kilometer-square grid level. In previous updates, direct estimates of income and vehicle access were used instead of relying on 2010 population counts for estimation.

For additional information, see Documentation.

How is the Food Access Research Atlas related to the Food Environment Atlas?

The Food Access Research Atlas maps and provides selected food access indicators for census tracts. The Food Environment Atlas provides a wider set of statistics on food choices, health and well-being, and community characteristics. While the Food Access Research Atlas provides information at the census-tract level, the smallest geographic level of data in the Food Environment Atlas is the county. The Food Environment Atlas also has an advanced query tool that allows users to identify and map counties sharing the same degree of multiple indicators.

Recommended citation

Economic Research Service (ERS), U.S. Department of Agriculture (USDA). Food Access Research Atlas, https://www.ers.usda.gov/data-products/food-access-research-atlas/

Food Access Research Atlas

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Last updated: Tuesday, January 17, 2017

For more information contact: Michele Ver Ploeg and Alana Rhone

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