SACRAMENTO, Calif.—California Insurance Commissioner Steve Poizner says workers compensation insurance rates will increase an average of 4% for 2010 coverage in the state.

Mr. Poizner, who made the announcement Wednesday, said the rate increase is based on recent rate filings by insurers that write 97% of the workers comp coverage in California.

Insurers that have filed to adjust their rates in 2010 include four companies that plan to reduce their workers comp rates by 1% to 8.4% and 42 companies that plan to increase their rates by 0.6% to 12%.

Companies that have not changed rates for 2010 do not have to file with the state.

A month ago, the commissioner rejected as “unwarranted” a Workers’ Compensation Insurance Rating Bureau of California request for a 22.8% increase.