The Consumer Federation of America's Bob Hunter -- the nation's leading independent insurance expert (actuary, former federal insurance czar, former Texas insurance commissioner) -- has a new report: State Automobile Insurance Regulation: A National Quality Assessment and In-Depth Review of California’s Uniquely Effective Regulatory System , 04/24/08 (109 page pdf). Here is an excerpt from the shorter news release.

[The report] found that rates have risen more slowly in the fifteen states that require insurers to receive advance approval of rate increases from the state. States with “prior approval” regulation also performed well in spurring competition and generating significant profits for insurers. The top-performing state in keeping rates down and providing comprehensive consumer protections was California.