# Method

1. Read every row of data/raw/npi_slim_202609.csv, a slim of the NPPES full replacement file of September 2026.
2. Keep entity type 1 (individuals). Drop rows with an NPI deactivation date and no reactivation date.
3. A row counts as a physical therapist when any of the 15 taxonomy slots holds a code whose NUCC 26.1 classification is Physical Therapist (225100000X and the ten 2251 specializations). Physical therapy assistants (225200000X) are counted on their own.
4. State is the practice location state on the record. Rows with a territory, foreign or blank state are in the total but not in the state table.
5. Per 100,000 uses the Census Bureau state population estimate for 1 July 2024 (NST-EST2024-ALLDATA).
6. Year is the NPI enumeration date. NPIs became mandatory for billing in 2007, so the 2006 and 2007 rows hold the people who were already in practice.