Data Methodology

Our Approach

The national and state-level auto insurance averages on this site are derived from two official sources: the NAIC Auto Insurance Database Report (published by the National Association of Insurance Commissioners) and the BLS Consumer Price Index for motor vehicle insurance (published monthly by the Bureau of Labor Statistics).

We use NAIC data as the base because it represents actual premiums paid by consumers, not quoted rates. The NAIC compiles this data from insurer financial filings across all 50 states and D.C. We then adjust for inflation using the BLS CPI to produce current-dollar estimates.

Why NAIC Data

The NAIC "combined average premium" is calculated from total written premiums divided by total written car-years (exposures). This captures what the full market actually paid, across all coverage levels, deductible choices, and discount programs. It is the most authoritative measure of what auto insurance actually costs in the United States.

The NAIC compiles data from insurer financial filings submitted to every state insurance department, covering virtually the entire private passenger auto insurance market. Because it measures actual paid premiums rather than quoted rates, the figures reflect real-world pricing including all applicable discounts.

The CPI Adjustment

The most recent NAIC data covers the 2023 calendar year (published June 2025). To produce a current estimate, we apply the change in the BLS Consumer Price Index for motor vehicle insurance from the 2023 annual average to the most recent available month.

State-Level Estimates

The same CPI adjustment is applied to each state's NAIC combined average premium. The NAIC publishes state-by-state data in the Average Premium Supplement. Each state figure is multiplied by the same CPI inflation factor to produce current-dollar estimates.

State-level "vs. national average" percentages are calculated against the CPI-adjusted national figure ($150/mo).

Why Estimates May Differ From Other Sources

You may notice that the cost figures on this site differ from averages published elsewhere. Several factors can explain these differences.

• What is being measured. Some sources report what a specific driver profile would be quoted today, while others (including the NAIC data we use) measure what consumers actually paid. These are fundamentally different metrics, and the gap between them can be significant.
• Coverage levels assumed. The coverage limits, deductibles, and optional coverages included in a cost estimate all affect the result. A "full coverage" average based on 50/100/50 limits will be higher than one based on 25/50/25.
• Driver profile. Age, driving record, credit score, vehicle type, and location all influence quoted rates. Estimates based on a 30-year-old with a clean record will differ from those based on a broader population average.
• Whether discounts are included. Real-world premiums reflect discounts for bundling, loyalty, safe driving, and other factors. Quoted rates may or may not account for these.
• Data vintage. Insurance costs change over time. An estimate based on 2023 data will differ from one based on 2024 or 2025 data, even after adjusting for inflation.
• Geographic granularity. The BLS CPI we use for inflation adjustment is a national index. Actual rate changes vary by state and even by zip code, so a uniform national adjustment is an approximation.

Our approach prioritizes transparency: we show the base data year, the inflation adjustment, and the sources behind every figure so you can evaluate the methodology yourself.

What This Does Not Include

• Age, credit, and driving record breakdowns come from commercial rate studies (noted on each data table) because the NAIC does not publish this level of detail.
• Minimum coverage averages use a composite of commercial rate studies because the NAIC does not separately report liability-only vs. full coverage premiums.

Where we use commercial sources, this is clearly labeled on the relevant data table.

Update Schedule

The BLS publishes new CPI data monthly. We update the CPI adjustment when new data becomes available. The NAIC publishes its Auto Insurance Database Report annually (typically in Q1, covering data from two years prior). When a new NAIC report is released, we update the base figures and recalculate all estimates.

Last updated: 2026-03-16