The biggest negative growth numbers occurred in midsize, compact and subcompact cars. Together, TrueCar numbers show, car companies have sold half a million fewer cars in those three categories in 2017 than in 2016.
"A lot of the car companies are split," said Jessica Caldwell, director of industry analysis for the auto research company Edmunds. "The truck and SUV business is doing decently, but they are struggling on the car side."
That could mean a limited life expectancy for cars that a decade ago were solid sellers for major companies. Kelley Blue Book's Brauer said he saw a doubtful future for the Hyundai Azera, Chrysler 300, Chevrolet Impala, Ford Taurus and Toyota Avalon.
"If my livelihood were depending on selling those cars, I'd be worried," Brauer said.
The shift from sedans to SUVs is harder on companies that have focused more on passenger cars. Kia, Hyundai, Acura, Chrysler, Buick, Dodge, Chevrolet and Ford numbers all fell from 2016 to 2017, in part because their vehicle mix leans more heavily toward sedans.
Chevrolet and Ford have booming truck segments, as their non-truck vehicle sales fell by 70,000 and 100,000 units this year, respectively.
That has required some quick pivoting. Chevrolet was able to fast-track its affordable Trax crossover when it saw buyers leaning toward SUVs because it already was building the Trax overseas for foreign markets.
"Two or three years ago, the small SUV segment was almost nothing, but we saw a hole in our portfolio and were able to fill it quickly," said Steve Majoros, the company's marketing director for cars and crossovers.
As a result, Majoros said, car buyers are getting out of Cruzes and into a Trax or out of Malibus and into an Equinox or Tahoe.
"We'll take a Malibu loss if the customer goes into a different Chevrolet," Majoros said.