The promise of the American dream has given many hope that they themselves could one day rise up the economic ladder. But according to a study released Tuesday, those already in financially-stable circumstances should fear falling down a few rungs too.

The study, by the Pew Charitable Trusts, found that nearly a third of Americans who were part of the middle class as teenagers in the 1970s have fallen out of it as adults. Though Pew examined only a certain demographic swath of participants, its findings suggest the relative ease with which people in the U.S. can end up in low-income, low-opportunity lifestyles—even if they started out with a number of advantages.

Though the American middle class has been repeatedly invoked as a key factor in any economic turnaround, numerous reports have suggested that the middle class enjoys less existential security than it did a generation ago, thanks to stagnating incomes and the decline of the industrial sector.

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