Methodology
How we source, process, and present housing data across OpenHousing.
Data Sources
| Source | Data | Update Frequency |
|---|---|---|
| Census ACS (1-Year) | Income, rent, demographics, tenure | Annual (September) |
| Census ACS (5-Year) | ZIP-level estimates, small geographies | Annual (December) |
| HUD CHAS | Cost burden by income, race, household type | ~2 year lag |
| HUD Fair Market Rents | FMR by county and metro | Annual (October) |
| FFIEC HMDA | Mortgage application data | Annual (March) |
| Zillow ZHVI | Home values by ZIP, metro, state | Monthly |
| Zillow ZORI | Observed rent index | Monthly |
| FRED (Federal Reserve) | Mortgage rates, HPI, economic indicators | Weekly/Monthly |
| BLS | Employment, wages by occupation | Annual/Quarterly |
| HUD PIT/HIC | Homelessness counts | Annual (June) |
| Census Building Permits | New construction permits | Monthly |
| Eviction Lab | Eviction filing data | Weekly |
Affordability Score
OpenHousing's affordability score (0–100) is a composite index that measures how affordable housing is in a given geography relative to local incomes. A score of 100 represents perfect affordability; 0 represents extreme unaffordability.
Components
- Rent-to-Income Ratio (30% weight): Median gross rent as a percentage of median household income. Benchmarked against the 30% affordability standard.
- Price-to-Income Ratio (25% weight): Median home value divided by median household income. Compared to the historical norm of 3.0x.
- Cost Burden Rate (25% weight): Share of renter households paying 30%+ of income on housing. Lower is better.
- Income-to-Mortgage Qualification (20% weight): Whether the median household income qualifies for a mortgage on the median-priced home at current rates (28% front-end DTI, 10% down, 30-year fixed).
Score Ranges
- 70–100: Affordable — Housing costs are manageable for most households
- 40–69: Moderate — Significant share of households face cost burden
- 0–39: Crisis — Majority of lower-income households are severely burdened
Update Frequency
OpenHousing data is updated on the following schedule:
- Monthly: Zillow home values and rents, mortgage rates, building permits
- Quarterly: Affordability scores, rankings, metro comparisons
- Annually: Census ACS data, HMDA mortgage data, HUD CHAS and homelessness data, BLS wage data
Limitations
- Census ACS data has a 1–2 year lag. Our most recent ACS data is from 2023.
- HUD CHAS data has a ~3 year lag and uses 5-year ACS estimates.
- PIT counts are acknowledged to undercount the homeless population, particularly unsheltered individuals.
- Zillow indices may not capture the full range of housing costs, particularly at the low end of the market.
- Our affordability score is a simplified model — individual circumstances vary widely.
Questions?
For questions about our methodology, data sources, or calculations, contact us at info@thedataproject.ai.