Nearly one-third of Americans think the middle-class will disappear eventually, according to a study by Northwestern Mutual released Tuesday.

At the same time 45 percent feel the middle-class is shrinking and only 21 percent think it is expanding, according to the latest data released from the 2018 Planning & Progress Study of 2,003 adults. The number of people who define themselves as middle-class went down slightly to 68 percent, compared to 70 percent in 2017.

“The middle-class is a cornerstone of our nation’s culture and identity,” said Emily Holbrook, director of planning at Northwestern Mutual. “Clearly people are losing optimism in its longevity.”

Although 60 percent of the study participants think movement into and out of the middle-class are possible, more think it is easier to move between the poor and middle-class than think it is possible to move between the middle-class and wealthy classes.

The majority of Americans, 78 percent, said assets under $100,000 would qualify one as middle class, with half saying the middle class stops at assets of $50,000 and anyone below that is poor. Most said work ethic and homeownership define the middle-class.