The nation's working middle class, commonly seen as the economic backbone of the nation, is now less than half of the U.S. population and continues to financially struggle under President Barack Obama, a new report warns.

The middle class “is declining and no longer constitutes a majority under President Barack Obama,” Breitbart News reported, citing a Pew Research Center study, which found that “after more than four decades of serving as the nation’s economic majority, the American middle class is now matched in number by those in the economic tiers above and below it.”

Middle class Americans now comprise less than half, or 49.9%, of the nation’s population, down from 61% in 1971, according to the Pew report. “The share living in the upper-income tier rose from 14% to 21% over the same period. Meanwhile, the share in the lower-income tier increased from 25% to 29%,” Breitbart reported.

For Pew, middle class Americans live in households earning between two-thirds to two times the nation’s median income. In 2014, that ranged from $41,900 to $125,600 for a three-person household.

Some 120.8 million adult Americans lived in middle-class households this year, according to Pew. That’s slightly less than the combined number of upper-income adults (51 million) and those at the lower tier (70.3 million).

While households across the spectrum have seen higher earnings over the past several decades, upper-income households have seen their pay rise the most, Bloomberg reported.

The median income of those families was $174,625 in 2014, up 47 percent since 1970, Pew data show. That compares with a 34 percent gain for the middle class and a 28 percent increase for the poorest households.

The "state of the American middle class is at the heart of the economic platforms of many presidential candidates ahead of the 2016 election," Pew researchers Rakesh Kochhar and Richard Fry wrote in their report. Meanwhile "a flurry of new research points to the potential of a larger middle class to provide the economic boost sought by many advanced economies."

And middle-income Americans have fallen further behind financially in the new century.

In 2014, the median income of these households was 4% less than in 2000. Moreover, because of the housing market crisis and the Great Recession of 2007-09, their median wealth (assets minus debts) fell by 28% from 2001 to 2013, Pew reported.

The middle class holds 43 percent of U.S. aggregate income, the smallest share in Pew’s data back to 1970.

Almost half of aggregate earnings in the U.S. is now commanded by the wealthiest families, who are "are on the verge of holding more in total income than all other households combined," Kochhar and Fry wrote. "This shift is partly because upper-income households constitute a rising share of the population and partly because their incomes are increasing more rapidly than those of other tiers."

The steady decline of the middle class is yet another sign of economic polarization, said Rakesh Kochhar, associate director of research at Pew. Not only are more Americans shifting into the upper and lower classes, but they are moving into the higher range of the upper class and the lower range of the lower class.

“There are fewer opportunities that place people in the middle of the income distribution,” Kochhar said.

To be sure, being a member of the middle-class has long been treated as an American badge of honor.

“For decades, the middle class had been the core of the country. A healthy middle class kept America strong,” experts and politicians told CNN Wire. “But more recently, these residents have struggled under stagnating wages and soaring costs. Presidential candidates on both sides of the political aisle are campaigning on ways to bolster the nation’s middle class and increase opportunities to climb the economic ladder,” CNN Wire reported.

Most Americans have traditionally identified themselves as middle class, even those at the top and bottom, reflecting a kind of cultural heritage tied to the American dream of self-reliance, The Sacramento Bee explained. “But the Great Recession and subsequent slow recovery have shaken that image.”

A recent Gallup poll showed that just 51 percent of U.S. adults considered themselves middle or upper middle class, with 48 percent saying they are part of the lower or working class.

Patrick Egan, a politics professor at New York University, says the Pew findings and the Gallup surveys suggest that the public may be more open to policies of redistribution.

"Americans are always kind of reluctant to embrace open-class warfare," Egan said. But "if more Americans are under the idea of placing themselves at the bottom, you'll see politicians follow," he told Tribune.

(Newsmax wire services contributed to this report).

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