Some experts, like Michael Sivak, director of Sustainable Worldwide Transportation at the University of Michigan Transportation Research Institute, argue that at least part of the drop is permanent and that it's part of a global decline in driving among young people. He contends that part of the shift is rooted in the growth of access to the Internet: Modern teens can connect with each other through social media, so there's less of a need to get together by driving to popular hangouts or by cruising.
"I believe that a large part of the drop is permanent," says Sivak, who was one of the first researchers to document the trend. "It's not just teens. It's people in their 20s and 30s, as well. When we asked people (in a new national survey of young adults without a license) when they planned to get a driver's license, 21.5% of all respondents said never; 35.4% of those aged 30-39 said never. That tells us that a large part of the drop we see is permanent."