Ten years ago, a record 17.6 million cars, trucks and SUVs were sold in the U.S. Some forecasts say the country might not come close to that number again.

Analysts at consulting firm Bain & Company said several signs indicate the market is about to shrink even more. Falling birth rates, behavioral changes, high car prices and a growing array of alternatives could drive sales down by more than 2 million units by 2040, according to their analysis.

These indications point to a future where automakers fiercely compete for a shrinking number of customers, said Mark Gottfredson, a partner at Bain & Company.

The auto industry has historically depended on an annual 1% growth rate that tracks the increase of the overall population, Gottfredson said. But all over the world, government statistics show population growth has slowed, and some countries are already seeing declines.

"It is the perfect storm, isn't it," Gottfredson said. "It starts with the population declines. You're no longer a growth industry. You're a declining industry. You're a declining industry at a time when the technology is disrupting everything."

The U.S. fertility rate in 2025 was about 1.6 births per woman. While not as low as some countries in Europe or Asia, it's considered below the replacement rate of 2.1, according to the Centers for Disease Control.

Bain said that has been offset by relatively high immigration — about a million people coming to the U.S., according to the historical average it cited. But the firm said it expects restrictive immigration policies will last for the next 15 years, cutting historical net migration rates of the past 20 years in half, which means it could again reach low levels seen in 2019.

That remaining population's behavior has changed — in part due to high prices and affordable alternatives, according to Bain. Half of 16-year-olds today don't have a driver's license, compared with nearly 70% of 16-year-olds between the years of 1966 and 1984, Gottfredson said. The stat might reflect a mere delay rather than a total refusal — Bain's research suggests most people still get licenses by age 25.

Still, the share of new vehicle registrations among people aged 18 to 34 fell from 12% in the first quarter of 2021 to under 10% by mid-2025, according to S&P Global Mobility. Buyers 55 and older account for nearly half of all new registrations and have held the largest share for eight straight quarters, the firm said.

"The engine behind it is affordability," said Craig Daitch, founder and president of Telemetry, a firm that does market research for the auto industry. New vehicle monthly payments are up 30% over four years, and nearly one in five new vehicles now carries a payment over $1,000 a month, he added.