Census block group geography

Block group is the Census geography one level below tract, and in this slice it is the resolution at which property-level location is published. FEMA's NFIP Redacted Claims v2 and Redacted Policies v2 on OpenFEMA both provide location as "state, ZIP, county FIPS, census tract, census block group and rounded lat/long" — the redaction ladder that replaces exact addresses. First Street Foundation's Climate Risk Data takes the same design choice from the modeling side, aggregating its property risk models to "state, congressional district, county, town, Census place, tract and block group." The practical consequence: joins, portfolio rollups and exposure estimates on these sources work at tract or block group, not at parcel or street address.

Buy this data expecting block-group resolution and you avoid the classic join failure: NFIP redacted claim and policy files give no exact parcel or address, only state, ZIP, county FIPS, tract, block group and rounded lat/long. Any workflow needing property-level precision — individual building exposure or address-level matching — needs a different source. First Street's seven-level aggregation ladder shows the same constraint on the climate-risk side.

Use these checks before you rely on a source's treatment of this term:

1. List the geography fields before buying: the NFIP redacted files publish state, ZIP, county FIPS, census tract, census block group and rounded lat/long — nothing finer.
2. Check coordinate precision: lat/long is rounded in the OpenFEMA redacted files, so distance-based analysis has a floor.
3. Confirm the aggregation ladder on modeled data — First Street publishes at state, congressional district, county, town, Census place, tract and block group.
4. Plan joins at tract or block group from the start, and treat any vendor claim of address-level matching on these sources as unverified.

Where to see it in context: property-casualty-insurance data.

• nfip-redacted-claims — the OpenFEMA claim file whose location fields stop at block group plus rounded lat/long.
• nfip-redacted-policies — the companion policy file with the same redacted geography fields.
• nfip-redacted-claims — the OpenFEMA claim file whose location fields stop at block group plus rounded lat/long — already listed above, and the primary place this geography appears in practice.