The so-called Gini index, which measures the distribution of wealth on a scale from 0 to 1, reached 0.485 in 2018, up from 0.482 in 2017 and higher than at any point since the agency began tracking it in 1967, when it stood at 0.397. A value of 0 would mean perfect equality.

In particular, income inequality rose markedly in Alabama, Arkansas, California, Kansas, Nebraska, New Hampshire, New Mexico, Texas and Virginia.

Democratic presidential candidates like Sens. Elizabeth Warren of Massachusetts and Bernie Sanders of Vermont have made economic inequality the centerpiece of their campaigns, with both proposing a tax on the wealth of the richest Americans.

Still, median household income is rising. It reached $61,937 in 2018, only the second year since the 2008 financial crisis that that figure has exceeded income levels prior to the crisis.

Wages have been growing above 3 percent since late 2018, while the inflation rate has stayed below 2 percent.

The percentage of Americans with incomes below the poverty level also dropped for the fifth consecutive year, declining to 13.1 percent in 2018 from 13.4 percent the year before.

“This is the story of a tight labor market, where more people have jobs and workers at the middle and bottom have enough bargaining power to get real wage gains,” Baker said. “Long and short, I see this as a mostly positive story — with the important qualification that we have a very long way to go to get to a situation where workers at the middle and bottom have a fair share of output.”