Methodology · v2.0 · June 2026
About the data behind this map.
Every layer in this tool is sourced from public data or NFP operational records. This page documents each source, its vintage, known caveats, and the transformations we applied to get it onto the map. Read this before citing a number in a grant proposal or a board meeting.
Data sources
The map harmonizes five datasets at two geographic grains — 2020 Census tracts (434 tracts) and 2020 ZCTAs — clipped to the 14-county Nashville MSA.
Census
American Community Survey · 5-Year Estimates
ACS 2020–2024- Variables
- Median household income (
B19013), poverty rate (B17001), total population (B01003), race/ethnicity (B03002) - Geography
- Census tract, 2020 vintage boundaries
- Retrieval
- Census Bureau API, pulled quarterly via the ACS ETL notebook
- Margins
- 5-year estimates have smaller margins than 1-year, but tract-level income can still have ±$8k–$15k error at 90% confidence
CDC
PLACES: Local Data for Better Health
CDC PLACES 2024 release- Variables
- Diabetes prevalence (crude, adults 18+)
- Geography
- Census tract — model-based small-area estimates
- Method
- CDC uses BRFSS responses + ACS covariates to produce tract-level prevalence. These are modeled, not measured.
- Caveat
- PLACES estimates are a smoothed surface. Do not interpret tract-level differences below ~1 pct point as meaningful.
USDA
Food Access Research Atlas
FARA 2019 · 2010 tract boundaries- Variables
LILATracts_1And10,lapop1,lalowi1, vehicle-availability flags- LILA definition
- Low-income tract where a significant share of residents are >1 mile (urban) or >10 miles (rural) from the nearest supermarket
- Boundary issue
- FARA uses 2010 tract boundaries. We crosswalk to 2020 tracts — see below.
- Next refresh
- USDA has not published a revised FARA since 2019. We flag this on the map.
CFMT
Giving Matters · Nonprofit Registry
Scraped Feb 2026- Records
- 1,045 middle-TN nonprofits with addresses and mission statements
- Geocoding
- Census Geocoder → fallback to Nominatim; 94.2% geocoded successfully
- Classification
- Mission statements run through Claude Haiku with a 16-category rubric (see below). Human-spot-checked at n=150.
- License
- Public registry data · Community Foundation of Middle TN
NFP
Partner Network · Internal Records
Jun 2026 snapshot- Records
- 43 active partner sites with meal-distribution programs
- Source
- NFP Operations CRM export, geocoded against Census
- Fields
- Partner name, address, partner type, program type
Processing pipeline
Raw sources land in /data/raw. They pass through a four-step pipeline before the map sees them.
Step 01
Ingest
Fetch from APIs or scraped registry; normalize column names; tag with vintage.
Step 02
Harmonize
Crosswalk geographies to 2020 tracts; uppercase GEOIDs to 11 digits.
Step 03
Classify
LLM categorizes nonprofit mission statements into 10 service categories.
Step 04
Publish
Write slim GeoJSON + indicator CSVs to
/public/data.USDA LILA 2010 → 2020 crosswalk
USDA's Food Access Research Atlas is still reported on 2010 census tracts, while every other dataset in this tool is on 2020 tracts. A direct join loses ~18% of tract-level LILA flags.
Our approach
- Start with the Census 2010→2020 tract relationship file (TIGER).
- Where a 2010 tract maps 1:1 to a 2020 tract, copy flags directly.
- Where a 2010 tract splits into multiple 2020 tracts, propagate the LILA flag to all children.
- Where multiple 2010 tracts merge into one 2020 tract, apply the flag if any parent was LILA (conservative — favors identifying need).
- Population variables (
lapop1,lalowi1) are apportioned by area-weighted overlap.
Caveat. This crosswalk introduces 3–6% error at the tract level. For county-level aggregates the error is negligible. For tract-level planning, treat LILA flags as indicative, not definitive.
Partner classification rubric
The 16 categories used for Giving Matters nonprofit classification:
| Category | Definition |
|---|---|
| school_summer | Programs serving K–12 students during school year or summer break |
| medical_health | Clinics, pharmacies, health screenings, mental-health services |
| transitional_housing | Short-term housing for people transitioning out of crisis |
| senior_services | Programs targeting adults 55+ |
| community_development | Neighborhood revitalization, economic development, community-building |
| homeless_outreach | Direct services for people experiencing homelessness |
| workforce_development | Job training, career counseling, skills education |
| after_school | Out-of-school-time programs for children |
| community_meals | Meal programs, food pantries, community kitchens |
| child_advocacy | CASA programs, child advocacy centers and child-welfare nonprofits serving children in the court or foster-care system |
| legal_advocacy | Free or low-cost civil legal services, and policy or advocacy groups on economic justice, housing, food access and related issues |
| veterans_military | Services, benefits navigation and community support for veterans, active-duty military and their families |
| faith_ministry | Congregations and faith-based organizations with no clear food, housing, health or other service specialization |
| environment_conservation | Land trusts, conservation, parks and greenspace groups, sustainability and active-transportation nonprofits |
| higher_education | Colleges, universities and their foundations (not K–12 schools or tutoring programs) |
| other | Orgs that don't fit the above or ambiguous mission text |
Evaluation. 150 randomly-sampled classifications were human-reviewed in March 2026.
Agreement with ground truth: 91.3%. The most confused pair is
community_meals ↔ homeless_outreach,
which often overlap in practice.
Glossary
| Term | Meaning |
|---|---|
| MSA | Metropolitan Statistical Area — the 14-county region centered on Nashville (OMB-defined). |
| GEOID | Unique identifier for a census geography. Tracts are 11 digits: STATE(2) + COUNTY(3) + TRACT(6). |
| LILA | Low-Income Low-Access — USDA designation for tracts that are both low-income and have low supermarket access. |
| ZCTA | ZIP Code Tabulation Area — the Census Bureau's spatial approximation of USPS ZIP codes. |
| ACS | American Community Survey — Census Bureau's ongoing demographic survey. |
| PLACES | CDC program producing model-based small-area health estimates. |
| Choropleth | A map where geographic areas are shaded by the value of a variable. |
Known caveats
- Vintage mismatch. USDA LILA is from 2019. ACS is 2020–24. CDC PLACES is 2024. We show the most recent available but readers should know they don't all describe the same year.
- Modeled vs measured. PLACES diabetes rates are modeled, not observed. Treat as a directional signal, not a count of cases.
- Suppressed tracts. ACS suppresses estimates for tracts with very small populations. These appear as "—" on the map.
- LILA boundary error. 3–6% tract-level error from the 2010→2020 crosswalk. See above.
- Partner registry is a snapshot. Giving Matters changes weekly; we refresh quarterly. Some listed orgs may have closed or merged.
- Not a census of food assistance. Not every food-providing org is in Giving Matters. Informal, church-based, and mutual-aid networks are under-represented.
Credits
Built by the Belmont Data & AI Collaborative in partnership with the Nashville Food Project. Geographies by the U.S. Census Bureau. Basemap by CARTO and OpenStreetMap contributors.
Questions, corrections, or data requests: data@belmont.edu.