# Method

Source: CMS NPPES full replacement file, September 2026 (latest enumeration date
2026-09-12); NUCC Health Care Provider Taxonomy code set 26.1.

- Rows with entity type 1 only. Deactivated NPIs carry no entity type on the file and drop out.
- Year and month come from the Provider Enumeration Date.
- One taxonomy per NPI: the first slot whose primary switch is Y, else slot 1.
- State is the practice location address state.
- Growth rankings include only classifications with at least 500 new NPIs in 2024.
- Medical residents usually register under the student code (390200000X) and change it later, so recent years undercount physician specialties.