Such unsustainable rents have resulted in more lower-income people moving out of the Los Angeles area than are moving in.

Not only are they being replaced by higher earners whose arrival pushes up housing costs in Los Angeles, but their relocation to less expensive areas of the state also tends to drives up costs in those communities.

“We get a lot of spill-out that comes from the Bay Area and L.A.,” said Amber Crowell, an assistant professor of sociology at California State University, Fresno. “And we expect it to get worse.”

This was not always the case.

In Southern California, as the region’s economy grew in the 1970s and 1980s, there was a symbiotic relationship between job growth and home construction. In those decades, the economy created a new housing unit for every three new jobs. The economy slowed down over the following 20 years, but the area still gained nearly a million more new homes.

The recovery from the most recent recession has played out differently. The job market has churned to life, but housing construction has slowed to a trickle. These days only one new housing unit is being built for every eight new jobs, and supply has fallen short of demand .

Mr. Garcia, of the Terner Center, said that in the years since the most recent recession, it had also become much more difficult to get a mortgage.