At the most basic level, initial ratemaking involves looking at the frequency and severity of insured perils and the expected average payout resulting from these perils. Thereafter an insurance company will collect historical loss data, bring the loss data to present value, and compare these prior losses to the premium collected in order to assess rate adequacy. Loss ratios and expense loads are also used. Rating for different risk characteristics involves at the most basic level comparing the losses with "loss relativities"—a policy with twice as many losses would therefore be charged twice as much. More complex multivariate analyses are sometimes used when multiple characteristics are involved and a univariate analysis could produce confounded results. Other statistical methods may be used in assessing the probability of future losses.
NerdWallet compared quotes from these insurers in ZIP codes across the country. Rates are for policies that include liability, collision, comprehensive, and uninsured/underinsured motorist coverages, as well as any other coverage required in each state. Our “good driver” profile is a 40-year-old with no moving violations and credit in the “good” tier.