The hubbub over the City Hall proposal to ban employee cafeterias in hopes tech workers will leave their cushy offices, mix with the masses on the sidewalks and patronize neighborhood restaurants has made its way to the East Coast, where the laughter can be heard almost from here.

I heard from an amused Alan Berube, a senior fellow at the Brookings Institution, a policy research center in Washington, D.C. For the past several years, Berube has published annual studies tracking American cities’ income inequality gaps.

San Francisco, you won’t be surprised to learn, is “an extreme version of the national pattern” when it comes to the rich getting far richer and the poor struggling to keep up, Berube said.

While Supervisors Ahsha Safaí and Aaron Peskin, the backers of the cafeteria ban, say it doesn’t target the tech industry, it’s hard to read it any other way, since tech companies are mostly the ones that offer free food to their employees. It’s easy to blame tech for the city’s ills — and income inequality is a huge one — but it’s City Hall that wooed tech companies here with tax breaks and didn’t get nearly enough housing built to accommodate their workers.

“I suppose that’s part of what’s behind arguments about whether tech companies ought to have cafeterias,” Berube said. “It does seem rather marginal compared to issues like affordable housing.”

Berube’s most recent findings, published earlier this year, contain a striking tidbit: San Francisco households at the 95th percentile of income bring in an astounding $507,824 every year. That means one out of every 20 households in San Francisco earns even more than that.

Just four years ago, Berube’s study showed San Francisco households at the 95th percentile were bringing in $353,576 every year. That means household income at that level has shot up $154,248 in just four years.

Not surprisingly, the $507,824 annual income is higher than households at the 95th percentile anywhere else in the country.

“It’s far higher,” Berube said. “It’s almost in a different universe.”

He pointed out that with San Francisco’s notorious dearth of children — we have fewer residents per capita who are younger than 18 than in any other major American city — those high-earning households are not generally supporting families of four or five people. On average, they’re supporting families of two.

Meanwhile, San Francisco households at the 20th percentile are bringing in $31,840, also higher than most other cities in the U.S. (I’d suspect that’s because our lowest earners have been priced out of the city altogether.)

With those at the 95th percentile making 15.9 times more than those at the 20th percentile, San Francisco has the sixth biggest income gap in Berube’s study. The most unequal city in America is Atlanta, where those at the 95th percentile make 18.1 times more than those at the 20th percentile.

“It’s getting worse,” Berube said of income inequality in this country. “Low-income households are gaining some ground, but even as they do that, households at the top in most big cities are pulling even farther away.”

Berube said inequality will always exist, but city leaders should be focused on how to ensure those at the bottom of the income ladder can move up. He said building more affordable housing and improving education are among the best ways to do that, which makes a lot of sense to me.

After all, it now costs $750,000 to build one unit of affordable housing in San Francisco, 17 percent more than it did just two years ago. There’s also a funding gap of $342,000 for each one of those units, meaning the amount not covered by bonds, state money or tax credits.

Meanwhile, public school teachers in San Francisco continue to be paid less than their counterparts in many other districts in California despite our city having the highest cost of housing in the state.

“Maybe the Board of Supervisors really is looking at the central issues affecting low and moderate income levels in San Francisco, but I suspect not,” Berube said. “You’re the City Hall reporter so you’d be able to say.”

I would, and I think you know my answer.

The severely mentally ill people we see on the sidewalks of San Francisco every day have one thing in common: The system failed them in disastrous fashion.

Chances are they have something else in common, too: mental illness stemming back to their childhood or young adulthood that was never properly treated. Clinical research shows 50 percent of all mental illness begins by age 14 and 75 percent begins by age 24.

State Sen. Scott Wiener, D-San Francisco, has a proposal to catch these cases far earlier, before people suffering with untreated schizophrenia and bipolar disorder wind up living on our sidewalks and under our freeway overpasses.

His legislation would strengthen oversight of California’s Mental Health Services Act, which was approved by voters in 2004. It imposes a 1 percent tax on personal income in excess of $1 million to fund county mental health programs. (Now there’s a real way to spread the wealth!)

Eighty percent of the money goes to treat those with severe mental illness, while 20 percent is supposed to go to intervention for those in the earliest stages, before it becomes disabling.

Wiener’s legislation targets that 20 percent, which is currently worth $500 million a year. It would provide more guidance into how counties must spend the money and more oversight of how the programs receiving the money are functioning. Currently, some counties are providing far better programs than others, and some aren’t even spending all their money.

“We need to help people avoid becoming severely mentally ill, chronically homeless people,” Wiener said.

Wiener has teamed with the Steinberg Institute, founded by Sacramento Mayor Darrell Steinberg, who as a state legislator championed the Mental Health Services Act.

Adrienne Shilton, government affairs director at the Steinberg Institute, said there’s no statewide strategy when it comes to prevention and early intervention of mental illness.

“What we see is 58 counties designing things in 58 different ways,” she said. “There is confusion, and we’ve heard this from the ground, about how to spend these dollars.”

Wiener said the legislation is a “bookend” to his other piece of legislation regarding the mentally ill, the one I told you about previously that would strengthen the state’s conservatorship programs.

Both bills have been approved by the state Senate and are currently pending in the Assembly’s Appropriations Ccommittee until Aug. 17. If they pass the committee, they’ll move to the Assembly floor for a full vote by Aug. 31. They’d then go to Gov. Jerry Brown, who’d have 40 days to sign them.

I’ll be sure to let you know what happens.

San Francisco Chronicle columnist Heather Knight appears Sundays and Tuesdays. Email: hknight@sfchronicle.com Twitter: @hknightsf