Theories abound to explain this shift. One emphasizes cost; it’s too expensive to own a car, especially after the high unemployment and meager wage gains of the Great Recession. Uber and other on-demand transportation services make this choice more practical.

Other theories focus on lifestyles and values. Young Americans “just don’t think driving is cool — or even necessary — anymore,” said Fortune magazine. Cars pollute, contributing to global warming. Millennials disapprove. They are said to prefer cities where they can walk, bike or use buses to get to stores, restaurants and jobs.

The most fascinating theory is that the Internet has displaced the automobile. Both are social instruments, it’s argued. Instead of going to the mall, teens and others stay in touch through social media and texting. It’s cheaper and more convenient.

Maybe. But a new study by Federal Reserve economists Christopher Kurz, Geng Li and Daniel Vine throws cold water on these and other generational explanations. It suggests that most potential young buyers couldn’t afford a new vehicle or didn’t want to incur the debt and operating expenses of doing so. Economic considerations dominated.