NerdWallet started with a list of the nation’s 25 largest auto insurance companies (by premiums written), compiled by the National Association of Insurance Commissioners using 2023 market share data. These companies collectively account for 88.1% of the market for private passenger auto insurance in the United States, according to the NAIC. Some of the providers are NerdWallet partners, but this did not influence our selection of the winner.

We narrowed the list to include only insurers that sell policies in a majority of states, that do not restrict availability based on membership criteria (such as military service) and for which pricing data was available for at least 20 states from Quadrant Information Services. Other companies that did not meet this data threshold may be cheaper for many consumers. We also eliminated companies that received more complaints to state regulators than expected for 2021-2023. Complaints received by state insurance regulators are reported to the NAIC, which calculates a complaint index each year for each subsidiary, measuring its share of total complaints relative to its size or share of total premiums in the industry. To evaluate a company’s complaint history, NerdWallet calculated a similar index for each insurer, weighted by market shares of each subsidiary, over the three-year period.