While tech cities San Francisco and San Jose had the biggest gains in median household income since the recession began, median household income in the 100 largest metro areas fell an average of 2.7 percent.
A major contributing factor to the divide is the demise of jobs and industries in slower-growing regions. Economist Robin Brooks says those job losses opened a gap between "red" states, which voted for Donald Trump in 2016, and "blue" states, which went for Hillary Clinton, per CBS News, with roughly 61 percent of blue state residents with jobs, compared with 59 percent in red states.
"There's definitely a pattern of the coasts pulling away from the middle of the country on income," said Alan Berube, an expert on metro US economies at the Brookings Institution. "There are a large number of places around the country that haven't gotten back to where they were 15 years ago, never mind 10 years ago."