# 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 chiropractor when any of the 15 taxonomy slots holds a code whose NUCC 26.1 classification is Chiropractor (111N00000X and the eleven 111N specializations). Physical therapists (Physical Therapist classification, 2251*) are counted on the same rules for comparison.
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 2005 to 2007 rows hold the people who were already in practice.
7. Sole proprietor is the "Is Sole Proprietor" flag the provider sets on the NPI record.