There are now 120.8 million adults living in middle-income households, the study found, compared with the 121.3 million who are living in either upper- or lower-income households.
— Rossbache (@Rossbache1) December 5, 2015
The report defines middle-income homes as earning between two-thirds and double the median household income, after incomes have been adjusted for household size.
In 2015, just under 50% of American adults lived in middle-income households, down from 54% in 2001 and 61% in 1971, the earliest year Pew looked at.
"The hollowing of the middle has proceeded steadily for the past four decades," Pew concluded.
At the same time, the share of income going to middle-income households has also fallen, from 62% in 1971 to 43% last year.
The lowest economic group rose from 16% to 20% of the population. The lower middle remained the same. The highest group went from 4% to 9%. The upper middle rose by 2 percentage points.
According to the study, the poverty rate of those 65 and over fell from 24.6% in 1970 to 10% in 2014. In contrast, there are more adults between 18 and 29 years now among lower income tiers.
