# Method

OEWS: BLS Occupational Employment and Wage Statistics, May 2025, cross-industry estimates, national_M2025_dl.xlsx and state_M2025_dl.xlsx. SOC 47-2152 covers plumbers, pipefitters and steamfitters together. OEWS counts wage and salary jobs and excludes the self-employed. Empty cells are suppressed by BLS.

California: Contractors State License Board list by classification, C-36 file, downloaded September 2026. Every row has status Clear. A licence belongs to a business; it can carry several classifications. "only_c36" counts licences whose sole classification is C36. Issue years count surviving Clear licences, not all licences ever issued.

Built with tools/report_plumbers_facts.py.