The middle class no longer dominates in the U.S.

Middle class Americans now comprise less than half, or 49.9%, of the nation's population, down from 61% in 1971, according to a new Pew Research Center report. 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.

For decades, the middle class had been the core of the country. A healthy middle class kept America strong, experts and politicians said.

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.

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