Wage stagnation. Rising housing prices. Loss of middle-class jobs. The looming threat of automation. These are some of the problems facing Stockton and its residents, but the city's mayor, Michael Tubbs, says his city is far from unique.

"I think Stockton is absolutely ground zero for a lot of the issues we are facing as a nation," Tubbs said.

Stockton is one of many Bay Area cities on the fringe of the wealth accumulating in Silicon Valley and San Francisco. The Central Valley city went bankrupt in 2012, and for decades it has been trying to diversify its agriculture-based economy.

"I feel that as mayor it's my responsibility to do all I could to begin figuring out what's the best way to make sure that folks in our community have a real economic floor," Tubbs said.

Tubbs is coordinating an effort to test a new way to sustain residents: universal basic income, or UBI. For one year, several dozen Stockton families will get $500 a month, no strings attached.

Dorian Warren co-chairs the Economic Security Project, which is contributing $1 million to the initiative. He said the goal is to gather data on the economic and social impacts of giving people a basic income.