The cost of the average car insurance policy last month was 20.3% higher than a year before, according to the Bureau of Labor Statistics. According to Bloomberg, it’s the highest one-year increase in insurance costs since 1976.

The average 6-month policy started in December cost Americans $780.28.

Related: How to Buy Car Insurance: Everything You Need to Know

Auto insurance showed a higher increase than any other element of the Consumer Price Index – the government’s primary measure of inflation. The index showed overall inflation of 3.4% over the same period.

Car insurance rates differ wildly by state, as state laws control liability in accidents.

Soaring Repair Costs

Soaring repair costs are the single largest factor driving insurance inflation. A New York Times analysis in July found that the average cost to repair a car after an accident has soared 36% in just five years.

Today’s increasingly high-tech cars often have expensive sensors in vulnerable places. The radar and lidar sensors that govern a smart cruise control system, for instance, need to sit on the exterior of a car to work properly. That leaves them susceptible to damage in even low-speed accidents.

Even a simple windshield replacement can now be a $1,000-plus repair thanks to embedded sensors and built-in lenses for traffic-scanning cameras.

Climate-Driven Disasters Also a Factor

A Washington Post analysis in September found that climate-related weather events also play a role.

Hurricane-prone Florida is the ultimate example. At least one prominent insurer – Farmers Insurance – recently elected to abandon the state entirely.

EVs More Expensive to Repair

Electric vehicles (EVs) are a small but growing percentage of the cars on American roads. Kelley Blue Book parent company Cox Automotive reports that 7.6% of the new cars Americans bought last year were electric – up from 5.8% in 2022 and 3.2% in 2021.

EVs can be more expensive to repair than gas-powered cars. The problem is particularly acute with Tesla products. Some studies have shown that other brands’ EVs are only marginally more expensive to repair than gas-powered cars, but Teslas are so costly to fix that insurers often write off even lightly damaged models.

High repair costs reportedly contributed to Hertz’s recent decision to divest much of its Tesla fleet.

The company has responded by launching its own insurance. But an insurance pool made up entirely of expensive-to-repair cars has its own problems.