Methodology

Every statistic rendered on Flood Figures is computed from public federal datasets and carried onto the page from the build's data files — no number is typed in by hand. This page documents the definitions, cleaning rules, and thresholds behind those computations, and the known limitations of each.

Data sources

• OpenFEMA FIMA NFIP Redacted Policies (v2) — the redacted federal record of NFIP flood insurance policy transactions, published by FEMA on OpenFEMA. Source of policy counts, premiums, coverage amounts, flood zone and occupancy distributions.
• OpenFEMA FIMA NFIP Redacted Claims (v2) — the redacted federal record of NFIP claims, also published on OpenFEMA. Source of claim counts, dollars paid, and loss-year series.
• GeoNames — city and ZIP code place names and the ZIP-to-city assignment (crosswalk), used under CC BY 4.0. FEMA's own city field is fully suppressed in the published datasets, so place naming relies on GeoNames.

Flood zone boundaries for specific addresses are not computed by this site; the authoritative source is FEMA's Flood Map Service Center.

What "policies in force" means here

A policy transaction is counted as in force when the build date falls on or after its effective date and before its termination date, and the policy has not been cancelled as of that date. This is an approximation reconstructed from transaction records: FEMA's official in-force statistics are compiled differently and will not match these figures exactly. Counts sum the policy-count field of qualifying records rather than counting rows.

Cleaning rules

• Records whose reported ZIP code is not a valid five-digit ZIP are dropped.
• Each ZIP is assigned to the state reported by the majority of its records; minority-state records within a ZIP are dropped.
• Records with a premium at or below zero, or above the 99.9th percentile of the build's scope, are dropped as data errors or extreme outliers. In the current build that percentile is computed within the covered states; a national build computes it nationally.

Premium vs. cost: two measures

Pages show both a premium figure (the policy premium alone) and a cost figure (premium plus federal fees and surcharges). The cost figure is closer to what a policyholder actually pays in a year; the premium figure is the cleaner measure of the insurance itself. Medians and means are computed over in-force policies.

Which ZIP codes get pages

A ZIP code receives a page when it has at least 100 policies in force or at least 50 recorded claims since 1978. The claims path exists so that places with substantial flood history but few current policies remain documented.

Small samples: premium statistics are suppressed

When a ZIP has fewer than 20 policies in force, its premium and distribution statistics (medians, means, zone and occupancy shares) are not rendered — a handful of policies cannot support a meaningful summary. Those pages show the policy count and the claims history only.

City and state roll-ups

City figures aggregate all ZIP codes that GeoNames places in the city — including ZIPs that do not meet the page threshold above and ZIPs with claims history but no current policies (post-office-box ZIPs among them). City totals therefore exceed the sum of the city's individual ZIP pages. State figures follow the same roll-up logic. Each state's city pages cover its largest cities by policies in force.

Claims figures

Claim counts and paid totals cover claims with a year of loss of 1978 or later. Paid totals sum building, contents, and increased-cost-of- compliance payments; the split is shown where available. Claims are attributed to years by year of loss, not by payment date.

Refresh cadence

The build is refreshed on the OpenFEMA publication cycle, roughly monthly. Every page footer states the data-as-of date of the build it was rendered from; the dates at the top of this page are the current build's.

What this site does not do

Flood Figures publishes descriptive statistics of the federal record. It does not predict flooding, model or score risk, estimate what any property would pay, quote or sell insurance, or recommend products. Where pages describe regulations — zone designations, the mandatory purchase rule, statutory coverage caps — they describe mechanisms verifiable from the cited public sources.

Known limitations

• In-force counts are approximations, as described above, and will differ from FEMA's official in-force statistics.
• Flood zone distributions reflect the zone recorded on each policy — including legacy designations from older map panels (numbered A and V zones, Zones B and C) — not current map boundaries or land area.
• The federal datasets are redacted for privacy; sub-ZIP geography is not available.
• ZIP-to-city assignment follows GeoNames and may differ from municipal boundaries or postal preferences in edge cases.