NumberResearchNumbering Change-Event Feed (Bitemporal Ledger)
Professional access · version 2026-09-18 (latest) · 28,733 rows · Members — internal use
Field-level changes observed between consecutive official files, recorded bitemporally: when we observed it vs the official file date vs the effective date.
Schema11 columns
| Column | Description |
|---|---|
| entity | nxx | block |
| npa | area code |
| nxx | prefix |
| block | thousands-block |
| change_kind | observed_added | observed_removed | field_changed |
| field | changed field |
| old_value | previous |
| new_value | current |
| observed_at | when we saw it |
| source_published_at | official file date |
| effective_date | official effective date |
Known limitations
The ledger began on 2026-09-18; nothing before that is reconstructed. Initial-assignee semantics apply.
Machine-readable catalog: /datasets.json · /data-sources.json. Cited versions never change — a version URL always resolves to the exact release. See methodology and licensing.