Understanding Food Access Data, PlainFoodAccess

A plain-language guide to what Census ACS food access indicators measure, how SNAP and poverty connect to food access, and what the data reveals about food insecurity across U.S. counties.

What the Data Measures

Food access data captures the relationship between where people live, what they can afford, and how easily they can reach nutritious food. PlainFoodAccess draws on two primary sources: the U.S. Census Bureau American Community Survey (ACS) and the USDA Economic Research Service Food Access Research Atlas.

The ACS collects self-reported data from millions of households each year, covering income, poverty status, SNAP participation, and vehicle access, all factors that shape whether a household can reliably obtain food. The USDA Atlas layers in geographic data about supermarket locations to calculate which census tracts qualify as "low access."

Key Indicators Explained

Low Access Population (%)

The share of county residents who live beyond the USDA distance thresholds from the nearest supermarket or large grocery store, 1 mile in urban areas, 10 miles in rural areas. A higher percentage indicates that more of the population faces a physical barrier to grocery shopping.

SNAP Participation Rate (%)

The percentage of households receiving Supplemental Nutrition Assistance Program benefits. This measures economic food access, the ability to afford food, rather than physical proximity to stores. Counties with high SNAP rates have large shares of residents who depend on federal nutrition support.

Poverty Rate (%)

The share of residents with income below the federal poverty line. Poverty is the root driver of food insecurity, households without sufficient income cannot purchase adequate nutrition regardless of what is available nearby.

Vehicle Access Rate (%)

The percentage of households with access to a vehicle. In areas where stores are distant, lack of vehicle access compounds the food desert problem. Households without cars rely on public transit, rideshares, or walking, all of which limit how much food they can carry and how often they can shop.

How SNAP and Poverty Relate to Food Access

Food access problems have two dimensions that are often conflated: physical access (can you reach a grocery store?) and economic access (can you afford food when you get there?). The data captures both.

Counties with high poverty rates and high SNAP participation but adequate store proximity still face serious food security challenges, residents can reach stores but may lack the income to fill a cart. Conversely, affluent rural counties may show large low-access populations simply because stores are far apart, without the poverty dimension that creates true food insecurity.

The most concerning counties are those where both dimensions align: remote locations with few stores and high poverty rates. These are the counties at the heart of the food desert problem.

What the Data Shows Nationally

Across 3,144 U.S. counties, food access challenges are widespread but unevenly distributed. Rural counties, particularly in the Deep South, Appalachia, the Mississippi Delta, and the Southwest, tend to show the highest combined stress: large low-access populations, high poverty, and limited vehicle access.

Urban counties present a different pattern. Dense cities generally have abundant grocery options within reach, but inner-city neighborhoods with high poverty can still face economic access barriers. SNAP participation rates in urban counties often reflect this: stores are nearby, but residents cannot afford to shop without assistance.

State-level patterns reflect both geography and policy. States with stronger SNAP outreach programs show higher take-up rates even at similar poverty levels. States with more dispersed rural populations tend to have higher low-access percentages.

Data Sources & Limitations

Census ACS 2024 5-Year Estimates: Survey-based data with margins of error, particularly for small counties. County-level figures are averages that can mask significant variation within counties.

USDA Food Access Research Atlas (2019): Based on supermarket locations at time of publication. Store closures and openings since 2019 are not reflected. The 1-mile/10-mile thresholds are arbitrary cut-offs, someone living 1.1 miles from a store in an urban area faces a different situation than someone 9 miles away in a rural county.

These limitations mean the data is best used for broad geographic comparisons and identifying counties at the extremes, rather than precise local planning.

Key takeaways

Food-access data combines the USDA Food Access Research Atlas with Census ACS indicators.
The Atlas measures distance to supermarkets and flags tracts that are both low-income and low-access.
See exactly how the figures are sourced and computed. Methodology

USDA low-access figures reflect the 2019 Food Access Research Atlas; socioeconomic context is the latest Census ACS 5-year (2024).

Frequently Asked Questions

What does "low food access" mean in Census data?

Low food access means a significant share of the population lives far from a supermarket or large grocery store, more than 1 mile in urban areas or more than 10 miles in rural areas. The Census ACS and USDA research capture the share of each county's population meeting this definition.

What is SNAP and how does it relate to food access?

SNAP (Supplemental Nutrition Assistance Program) provides monthly food benefits to low-income households. High SNAP participation rates in a county generally signal that a substantial portion of residents cannot afford adequate food without assistance. Counties with high SNAP rates often, but not always, overlap with food desert areas.

How does poverty connect to food access problems?

Poverty is the single strongest predictor of food insecurity. Households below the poverty line spend a much higher proportion of income on food, leaving little buffer when prices rise or income fluctuates. In counties where poverty rates exceed 20%, food access challenges tend to compound, stores may not locate in low-income areas because margins are thin, further limiting options.

Does low food access always mean a food desert?

Not necessarily by the strict USDA definition. The USDA Food Access Research Atlas classifies census tracts as "low access" based on distance to stores and income thresholds. A county can have pockets of food desert tracts alongside well-served areas. County-level averages smooth over this variation, looking at tract-level data within a county gives a more precise picture.

What time period does the data cover?

PlainFoodAccess uses Census Bureau American Community Survey (ACS) 5-Year Estimates, which pool five years of survey data to improve reliability for small geographies. The current dataset reflects the 2024 ACS 5-Year Estimates (covering 2020–2024). USDA Food Access Research Atlas data was last updated in 2019.

Why do some counties show high low-access populations but low SNAP rates?

SNAP participation depends on both eligibility and take-up rates. Some counties have populations that qualify for SNAP but do not enroll due to stigma, limited outreach, immigration status concerns, or complex application processes. Rural agricultural counties sometimes show low SNAP rates even with high poverty because seasonal farm workers are underrepresented in ACS surveys.

According to the U.S. Department of Agriculture Economic Research Service Food Access Research Atlas (2019 edition), 9,228 of roughly 71,700 U.S. census tracts meet the food-desert threshold. PlainFoodAccess pairs that tract-level data with the U.S. Census Bureau American Community Survey 2024 5-Year Estimates, released in December 2025, to build the county and state profiles described above; the full pipeline is documented in our methodology.