The scruffy-looking urban studies professor at Chapman University in Orange, Calif., has been studying and writing on demographic and geographic trends for 30 years. Part of California’s dysfunction, he says, stems from state and local government restrictions on development. These policies have artificially limited housing supply and put a premium on real estate in coastal regions…

A worker in Wichita might not consider those earning $250,000 a year middle class, but “if you’re a guy working for a Silicon Valley company and you’re married and you’re thinking about having your first kid, and your family makes 250-k a year, you can’t buy a closet in the Bay Area,” Mr. Kotkin says. “But for 250-k a year, you can live pretty damn well in Salt Lake City. And you might be able to send your kids to public schools and own a three-bedroom, four-bath house.”

According to Mr. Kotkin, these upwardly mobile families are fleeing in droves. As a result, California is turning into a two-and-a-half-class society. On top are the “entrenched incumbents” who inherited their wealth or came to California early and made their money. Then there’s a shrunken middle class of public employees and, miles below, a permanent welfare class. As it stands today, about 40% of Californians don’t pay any income tax and a quarter are on Medicaid.

It’s “a very scary political dynamic,” he says. “One day somebody’s going to put on the ballot, let’s take every penny over $100,000 a year, and you’ll get it through because there’s no real restraint. What you’ve done by exempting people from paying taxes is that they feel no responsibility. That’s certainly a big part of it.