CarInsurance.com quotes and sells both six (6) month premiums and twelve (12) month premiums on their website and through their call center. Depending on the state and carriers, you have the option of purchasing a 6 month policy or a 12 month policy.
In order to give an accurate comparison the CPI reports the lowest average annual car insurance rates quoted to consumers that compare rates at CarInsurance.com. If the premium was displayed as a 6 month policy, CPI annualized the premium for comparison. CPI includes rates that consumers viewed, but didn't necessarily purchase. The CPI reports on rates that come from auto insurance quotes consumers receive from CarInsurance.com Partners in 49 states and the District of Columbia.
CPI is a broad indicator of pricing activity in the personal auto insurance marketplace, it is not a comprehensive index as it reflects only the quotes of companies CarInsurance.com represents inthe 49 states plus the District of Columbia.
The CPI study also reports on historical car insurance premiums. These are annual (annualized) averages, even though the quotes presented may be 6 month premiums.
You can also get more state related CPI data in your state of California.