The once dominant middle class is losing its ground in the United States, and is no longer the economic majority after over four decades of holding the position.

Middle-class Americans now take up less than half, or 49.9 percent, of the population of the country, with the percentage declining since it was 61 percent in 1971, according to a new report by the Pew Research Center.

Pew defines middle-class Americans as those who live in households that earn anywhere between two-thirds and twice the median income in the United States. For 2014, the range was from $41,900 to $125,600 for a household of three people.

According to politicians and experts, a healthy middle class was the reason for keeping the country strong. However, soaring costs and stagnating wages have made it more difficult for the middle class, and presidential candidates from both sides are campaigning with promises to boost the middle class of America with opportunities to move up in their economic status.

Pew associate director of research, Rakesh Kochhar, said the decline of the middle class from 1971 is a sign of economic polarization – wherein more Americans are shifting from the middle class into the upper and lower classes. In addition, the movement of the population to higher ranges of the upper class and the lower ranges of the lower class is a mark of income inequality.

Over the same period that the middle class declined, the aggregate household income of the country has moved from middle-income to upper-income households. In 2014, 49 percent of the aggregate income of America went to upper-income households, compared to only 29 percent in 1970. In comparison, the middle class now only has 43 percent of the aggregate income, compared to 62 percent in 1970.

Kochhar explained that there are fewer chances for people to be placed in the middle class, but mentioned that more Americans are moving up the economic ladder than moving down.