The WCIRB California's 2023 State of the System Report revealed that shares of self-insurance vary widely by industry and are relatively low in most cases.
From the WCIRB:
“Estimated shares of self-insurance vary widely by industry and are relatively low in most industries.
The Public Administration and Education industries account for the majority of all self-insured employment in California.
Self-insured shares of employment by industry showed little change over the past year.”