The Gini index, a common measure of the inequality between the lowest and highest earners in a society, rose in America for the first time in ten years, according to data from the U.S. Census Bureau.

The Gini index, which ranges from 0 to 1, where 0 represents total income equality, rose 1.2% to 0.494 in 2021, the Census Bureau reported Tuesday. The increase was driven primarily by a measurable decline in the overall inflation-adjusted earnings of the poorest 10% of American households, with the richest 10% seeing no statistically significant changes in their overall income. (RELATED: Americans Are Still Getting Poorer Under Biden, Data Shows)

The poorest 10% of households saw their real incomes decline to $15,660 at most in 2021, almost 4.5% less than they made in 2020, according to the Census Bureau. The richest 10% of households made 13.53 times as much, making at least $211,956, up from 12.9 times as much in 2020.