Data sources
Where the numbers come from
Every dataset that powers a number on this site, with refresh cadence, vintage, and known limitations. We'd rather hide a field than fabricate one — if the source doesn't cover a ZIP, the section that depends on it is omitted from that page.
Data as of April 2026
Zillow Home Value Index (ZHVI)
- Purpose
- Typical home value for every ZIP, smoothed and seasonally adjusted.
- Refresh cadence
- Monthly. The site refreshes within a week of each release.
- Current vintage
- May 2026 (or latest available at refresh).
- Known limitations
- ZHVI is a model of typical home value, not an appraisal. It tracks the 35th–65th-percentile home, so very-high and very-low priced ZIPs in a market are compared on the same scale.
- License & attribution
- © Zillow Group, Inc., used under Zillow's Research Data terms (free non-commercial redistribution permitted with source attribution).
Zillow Observed Rent Index (ZORI)
- Purpose
- Typical asking rent for every ZIP with sufficient listing volume.
- Refresh cadence
- Monthly.
- Current vintage
- May 2026.
- Known limitations
- Some rural and very-small ZIPs have no ZORI because the sample is too thin. We hide rental metrics on those pages rather than estimate.
- License & attribution
- © Zillow Group, Inc., used under Zillow's Research Data terms.
US Census Bureau, American Community Survey (5-year)
- Purpose
- Population, median household income, aggregate real-estate-tax data for the effective property-tax rate.
- Refresh cadence
- Annual.
- Current vintage
- 2019–2023 5-year estimates (the latest published).
- Known limitations
- ACS suppresses estimates for very small ZIPs to protect respondent privacy. Those values show as 'data not available' rather than zero.
- License & attribution
- U.S. federal public-domain data. No license restrictions on redistribution.
FEMA National Risk Index
- Purpose
- Natural-hazard risk ratings (overall, riverine and coastal flooding, wildfire, drought, heat wave, hurricane, tornado, earthquake, winter weather).
- Refresh cadence
- FEMA releases new versions periodically. Pinned to release v1.20.
- Current vintage
- Release v1.20.
- Known limitations
- Ratings are county-level. Every ZIP in a county receives the same rating; intra-county variation (e.g. one floodplain ZIP, one bluff-top ZIP) is not captured. Parcel-level climate projections require First Street or similar paid data.
- License & attribution
- U.S. federal public-domain data.
IRS Statistics of Income — county-to-county migration
- Purpose
- Net migration of households between counties, derived from year-over-year address changes on tax returns.
- Refresh cadence
- Annual, with roughly an 18-month lag.
- Current vintage
- Tax year 2022 → 2023.
- Known limitations
- Aggregate county-level only. Returns ≠ people (a return can be a couple, a family, or a single filer). Counties with fewer than 10 inflow/outflow returns are suppressed for privacy.
- License & attribution
- U.S. federal public-domain data.
NCES Common Core of Data
- Purpose
- Open public schools — name, level, grade range, district, and enrollment.
- Refresh cadence
- Annual.
- Current vintage
- 2023–24 school year.
- Known limitations
- Public schools only; private and charter-but-not-public-funded schools are excluded. School ratings are not part of CCD — we do not show ratings unless a separate licensed source is available.
- License & attribution
- U.S. federal public-domain data.
US Census Bureau — Geography (ZCTA Gazetteer, ZCTA→County, ZCTA→Place)
- Purpose
- The canonical ZIP universe, geographic hierarchy (state, county, metro, city), and centroid lat/lng.
- Refresh cadence
- Updated annually.
- Current vintage
- Census 2020 boundary file + 2024 Gazetteer.
- Known limitations
- Census Zip Code Tabulation Areas (ZCTAs) approximate USPS ZIP codes; they don't match perfectly in every case (the USPS reorganizes ZIPs more often than Census redraws ZCTAs).
- License & attribution
- U.S. federal public-domain data.
HUD-USPS ZIP Code Crosswalk
- Purpose
- ZIP-to-census-tract, ZIP-to-county-subdivision, and ZIP-to-CBSA mapping used to translate between USPS ZIP boundaries and the Census geography hierarchy where the ZCTA file disagrees or lags.
- Refresh cadence
- Quarterly.
- Current vintage
- Q1 2026.
- Known limitations
- Like ZCTAs, the crosswalk reflects a point-in-time snapshot of the USPS ZIP universe; very-new ZIPs (introduced after the last release) won't appear until the next quarterly file.
- License & attribution
- U.S. federal public-domain data.