Model v3 · July 2026
How the Bolthole Index is scored
The Bolthole Index scores every U.S. county 0–100 as backup land: somewhere reachable, private, self-sufficient, administratively quiet, and cheap to hold for years. It is not a livability index — jobs, broadband, and nightlife score nothing here. Every input is public data or our own county-by-county legal research, and every formula below ships in the site's open build pipeline.
The six factors
Water (rainfall adequacy saturating at ~34in/yr, drought history, groundwater depth, perennial surface water), soil productivity (USDA NCCPI) with growing-climate usability, usable woodland and standing biomass (USFS FIA), energy independence (solar resource + how normal wood/propane heating already is, from ACS), and working-farm normalcy (USDA Census of Agriculture).
Distance to the nearest city of 100k+ (Census gazetteer great-circle), population density, total county population, and a small wooded-cover modifier. Percentile-ranked nationally.
FEMA National Risk Index expected annual loss per dollar of exposure (not the raw risk score, which mostly measures emptiness), drought exposure, extraction and federal-land pressure, and cooling-climate burden.
The county’s own scouted legal regime — residential building permit, county-wide zoning, owner-builder exemption — verified against official county and state sources (65%), plus state build/land/water rules: building-code regime, statewide land-use preemption, water rights, rainwater and greywater rules, right-to-farm, cottage food (35%).
State homestead exemption strength (asset protection for the land itself) and the Cato Institute’s Personal Freedom percentile — will the state mostly leave a quiet person alone.
Land price per acre and home values on saturating bands — cheap enough is cheap enough; cheaper adds little — plus state property and income tax burden and a hazard-loss insurance proxy.
How the composite works
- Weakest link wins. The headline score is a weighted geometricmean, so a county can't average away a fatal flaw — no water or zero seclusion drags the whole score down. Hard caps reinforce it: a county with near-zero seclusion or failing self-sufficiency is capped no matter how strong the rest looks.
- Percentiles for relative quantities, real-world bands for absolute ones. Density or land price are ranked against all 3,143 counties. Physical thresholds stay physical: rainfall adequacy saturates around 34in/year — 55 inches of Gulf humidity is not a better bolthole than 38 inches in the Ozarks.
- Missing data never scores. If a source has no reading for a county, that component drops out and its weight redistributes — we never fill gaps with invented averages. Each county page reports its data coverage.
- The scale is calibrated for legibility. Averaging six factors that trade off against each other (remote counties are rarely also wet, safe, and cheap) compresses raw composites into a narrow middle band. We stretch the final score linearly around the national median so differences are readable. Rankings are completely unaffected — it is the same order, on a wider ruler, and no county reaches a fake 100.
- Cheapness is deliberately light (5%). Price is a filter, not a virtue — an index that rewards cheap land ends up measuring poverty, not refuge. Carry cost also saturates: once land is affordable, cheaper stops adding points.
- No politics. Election returns feed nothing. Legal reality — permits, zoning, water rights, taxes — feeds a lot.
Data sources
| Source | Feeds | Vintage |
|---|---|---|
| County legal scout (first-party) | Building permits, zoning, owner-builder, septic authority for all 3,143 counties, cited to official county/state pages | 2026, ongoing |
| FEMA National Risk Index | Expected annual loss rate (hazard durability) | 2023 release |
| NOAA nClimDiv county normals | Annual precipitation and mean temperature | 1991–2020 normals |
| U.S. Drought Monitor | Share of weeks in severe drought | 2000–2025 |
| USGS groundwater + streamflow | Observed depth to water, perennial surface flow | latest year |
| USGS national water-table model (Zell & Sanford 2020) | Modeled depth to water for every CONUS county | 1985–2015 average |
| USDA NCCPI (soil productivity) | Cropland productivity index | current SSURGO |
| USFS Forest Inventory & Analysis | Forestland, timberland, standing biomass per county | 2015–2019 estimates |
| USDA Census of Agriculture | Farm counts, sizes, land values | 2022 |
| PAD-US 4.1 | Federal land share by county | 2024 |
| USGS MRDS + EPA ECHO | Mineral deposits; regulated oil/gas facilities (extraction pressure) | latest |
| ACS B25040 heating fuel + NREL solar summaries | Wood/propane heating share; solar resource (GHI) | ACS 2019–2023; NSRDB 1998–2009 |
| Zillow ZHVI | Typical home value by county | monthly |
| Cato Institute — Freedom in the 50 States | Personal Freedom percentile | 2023 edition |
| Tax Foundation / Lincoln Institute | State property, income tax, homestead exemption tiers | 2024–2026 |
| Census population + gazetteer | Population, density, metro distances | 2023 estimates |
Known limitations
- Western water is better covered than it was, not perfect. A calibrated national water-table model now gives every CONUS county a depth-to-water reading, but the model is a 1985–2015 average: pumping depletion (Ogallala, Central Valley) reads shallower than current reality, and water rights — who is legally allowed to use the water — are still only captured at the state level.
- County legal data is best-effort. Every record cites an official source and carries a confidence level, and we adversarially re-verify samples — but 3,143 counties change their rules constantly. Treat it as a scouting report, not legal advice, and verify locally before you buy.
- State-level inputs are uniform within a state.Homestead exemptions, tax tiers, and state-law factors can't distinguish two counties in the same state; county-level inputs do that work.
- No energy factor yet. Solar resource, heating-fuel norms, and grid independence are on the roadmap.
- Puerto Rico is excluded — too many missing sources to score honestly.
Versions
v3 · Jul 2026 — six-factor weighted model; woodland/biomass added; precipitation saturation; state-law double-counting removed; fatal-flaw caps; median-anchored display calibration.
v2 · Jul 2026 — exposure-normalized hazard loss; percentile normalization; county legal layer wired into scoring; geometric-mean composite.
v1 · Jun 2026 — first public release, seven equal-weight sub-scores.