The CarInsurance.com Premium Index tracks car insurance trends. With the number of online car insurance shoppers rising each month, CarInsurance.com offers this tool to show auto insurance premiums and customer rate trends. It is necessary to shop regularly because the same rate last year is not the same rate this year. Insurance companies regularly file new rates and shoppers are able to compare them at CarInsurance.com. CPI is a great tool to help you see the national average, along with state by state comparisons of average auto insurance premiums.