SourcesThe data family
housingdata.dev
A free, keyless copy of FHFA's county and state house price index and the Census Bureau's county building permits, in one format with versions you can cite.
What it is
housingdata.dev republishes two federal housing series: the Federal Housing Finance Agency’s House Price Index (HPI) and the Census Bureau’s Building Permits Survey. It serves them as plain JSON, CSV and Parquet files behind one API, with no key or signup. Like this site, it’s run by Eric Ness, so read this page as a description of a sibling, and check it the way you would any other source.
The site doesn’t produce any numbers itself. Each dataset names its source, its license and an exact credit line.
What it measures
- House prices by county and state (
house-prices). FHFA’s annual all-transactions index for every county and state with enough sales, from 1975 to 2025. Columns are the index itself, the change from the year before in percent, and two rebased versions set to 100 in 1990 and in 2000. The rebased columns are what make places comparable: FHFA’s own index starts at 100 in the first year it recorded each area, so raw index levels from two counties don’t line up. - Building permits by county (
building-permits). New housing units authorized by building permits in every county each year from 1990 to 2025, with state and national totals. Columns split units by building size (one unit, two, three or four, five or more), and give the number of buildings and the construction value on the permits in nominal dollars.
What the .dev layer adds is mostly packaging: one file layout, one set of place IDs (us-county- plus the five-digit FIPS code), the rebased index columns, and version IDs with fixed URLs for older versions. Both datasets update yearly; the site checks for new source data every seven days and validates each update before publishing. It also keeps counties that no longer exist, such as Connecticut’s former counties, as separate places with notes on when they ended.
What it misses
The price index covers only part of the market. FHFA builds its index from mortgages that Fannie Mae and Freddie Mac bought or guaranteed. Those are conforming, conventional loans, so the index leaves out homes bought with cash, jumbo loans and government-backed loans such as FHA and VA. FHFA’s flagship sample also leaves out condos, co-ops and multi-unit properties. FHFA publishes a separate expanded-data index that adds some of these sales, but this site doesn’t carry it.
It tracks change, not price. The HPI is a repeat-sales index: it compares the same homes when they sell or refinance again. FHFA says the index values on their own have little meaning, so it can tell you that prices in a county roughly doubled since 2000, but not what a typical home costs there.
The all-transactions index mixes in appraisals. Besides sale prices, it uses appraised values from refinances. FHFA labels the annual county and state indexes “developmental.”
Old values get revised. FHFA revises past index values as new repeat sales and refinances come in. A number you pulled last year may differ from today’s.
Small counties can have gaps. The index is only published where there were enough transactions. Where the sample was too small, the value is empty.
A permit is not a house. The Building Permits Survey counts authorizations, not construction starts or finished homes. Starts and completions come from a separate Census survey, the Survey of Construction.
Permits miss places that don’t require them. The survey covers only permit-issuing places. The Census Bureau puts construction outside those places at under 1 percent of new private housing nationally, but says the share varies by state and metro area.
Some permit numbers are imputed. Not every place reports. For the final 2025 annual estimate, about 91 percent of the housing-unit total was based on reported or equally good data; the rest was filled in by imputation. Construction values on permits often differ from what building actually costs.
The .dev layer has its own limits. It carries only the annual all-transactions index, not FHFA’s quarterly, monthly, purchase-only, metro or ZIP code series, and only annual permits, not monthly ones. It is a copy. For anything high-stakes, check the figure against FHFA’s or the Census Bureau’s own files.
How to access it
1Browse the catalog
Open housingdata.dev/datasets for the list, or ask the API:
curl -s "https://api.housingdata.dev/v1/catalog"
The catalog gives each dataset’s ID, current version and coverage.
2Read a dataset’s metadata
https://api.housingdata.dev/v1/{dataset} returns the version, coverage, source, license, credit line and download links. For example, https://api.housingdata.dev/v1/house-prices.
3Get one series for one place
The pattern is /v1/{dataset}/{series}/{location}.csv (or .json). This call returns the price index for Los Angeles County:
curl -s "https://api.housingdata.dev/v1/house-prices/all-transactions/us-county-06037.csv"
Tested on November 14, 2026, it returned one row per year from 1975 to 2025, with columns date, annual_change, hpi, hpi_1990 and hpi_2000. For national permits, use /v1/building-permits/permits/usa.csv; that call returned rows from 1990 to 2025.
4Download a whole dataset
/v1/{dataset}/download/{dataset}.csv (or .parquet) gives every place in one file, such as https://api.housingdata.dev/v1/building-permits/download/building-permits.csv.
5Pin a version
Add @ and a version ID after the dataset ID, and the URL will always return the same data. /v1/{dataset}/versions lists the current version and the monthly snapshots. The docs and the API reference cover caching, errors and every endpoint.
How to cite it
Cite the agency that produced the numbers and the exact version you used.
The site’s Sources page gives a credit line for each source, and its docs say to cite the monthly snapshots, which are kept permanently. Other versions may be removed after 30 days. Find the snapshot ID with /v1/{dataset}/versions.
A worked example for the Los Angeles County index:
Federal Housing Finance Agency, House Price Index (all-transactions, annual, developmental county and state indexes), https://www.fhfa.gov/data/hpi. Accessed via housingdata.dev, dataset house-prices, version 2026-11-06.946bd71618: https://api.housingdata.dev/v1/house-prices@2026-11-06.946bd71618/all-transactions/us-county-06037.csv. Retrieved November 14, 2026.
For permits, the credit line is “U.S. Census Bureau, Building Permits Survey, annual county files,” followed by the file URL the Sources page gives. Since FHFA revises past values, the version ID is what lets a reader get the same numbers you did.
Sources & further reading
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