WASHINGTON — The middle class is receiving less of America’s total income — its smallest share in decades — as wages stagnate and wealth gets concentrated at the top.
A study released Wednesday by the Pew Research Center highlights diminished hopes, too, for the roughly 50 percent of adults defined as middle class, with household incomes from $39,000 to $118,000. The report describes this group as suffering its ‘‘worst decade in modern history,’’ having fallen backward in income for the first time since World War II.
Most middle-class Americans say they have been forced to reduce spending in the past year. And fewer believe that hard work will allow them to get ahead. Families are more likely to say their children’s economic future will be the same or worse than their own.
In all, 85 percent of the middle-class Americans surveyed say it is more difficult than a decade ago to maintain their standard of living. Some 62 percent say a lot of the blame lies with Congress. A slight majority say a lot lies with banks and other financial institutions.
‘‘The job market is changing, our living standards are falling in the middle, and middle-income parents are now afraid that their children will be worse off than they are,’’ said Timothy Smeeding, a University of Wisconsin Madison economics professor.
He said that many middle-income families have taken a big hit in the past decade as health care costs increase, mid-wage jobs disappear,and college tuition rises. The more affluent families have fared better because they depend less on home values, which remain shriveled after the housing bust. Wealthier Americans are more likely to be invested in stocks.
‘‘No matter who is president, the climb back up for the middle class and the recovery will be slow and often painful,’’ Smeeding said.
The Census Bureau reported last year that income fell for the wealthiest — down 1.2 percent to $180,810 for the top 5 percent of households. But the bottom fifth of households — those making $20,000 or less — saw incomes decline 4 percent.
The new study says “middle class’’ makes up about 51 percent of US adults, down from 61 percent in 1971.
Since 2000, the median income for the middle class has fallen from $72,956 to $69,487.
The survey involved telephone interviews with 2,508 adults and was conducted from July 16 to 26.