Brookings Institution research confirms that the San Francisco Bay Area has the highest income inequality levels in the United States.

Brookings develops income inequality multiples for America’s 100 largest metropolitan areas by dividing the income earnings of the top 5 percent of households by the income earnings of the lowest 20 percent of households.

In 2014, the San Francisco metropolitan area was the only Northern California region to be in the nation’s top 10 for income inequality. With the top 5 percent of households making an average of $353,483, and the lowest 20 percent of households making $31,761, the income inequality ratio was 11.1, the third-highest income inequality in America.

Two years later, in 2016, San Francisco’s income inequality was still the third highest, at a ratio of 11. But the San Jose metropolitan area had jumped from the 17th highest rate of income inequality in 2014 to the 6th highest rate in 2016. With the top 5 percent of households making an average income of $428,363 and the lowest 20 percent of households making an average income of 40,807, the income inequality ratio was 10.5.

The San Jose metropolitan area’s top 5 percent of household incomes were second only to Bridgeport, Connecticut, with a household income average of $485,657. But San Jose’s lowest 20 percent was the highest average metropolitan household income for the nation’s lowest 20 percent of household incomes.

The Bay Area’s combined two metropolitan areas encompass the counties of San Francisco, San Mateo, Alameda, Contra Costa, Marin, and Santa Clara. With a combined income inequality ratio of about 10.8, there are no two adjoining metropolitan areas that come anywhere close to the inequality of the Bay Area. The gap between the highest earning group and the lowest group of earners expanded by a stunning $54,000.

In 2015, PolitiFact found that of the Brooking’s study’s 10 most unequal cities, 9 had Democratic mayors, including “Atlanta, San Francisco, Boston, Washington, New York, Dallas, Chicago, Los Angeles, and Minneapolis. Only one, Miami, has a Republican mayor.”