People are generally slow to acknowledge downward mobility. Many regard themselves as middle class even if their incomes fall well above or below the average. Experts say the rise in Americans who feel they've slipped below the middle class suggests something deeply rooted.
More people now think "it's harder to achieve" the American dream than thought so several decades ago, said Mark Rank, a sociology professor at Washington University in St. Louis.
Three years ago, Kristina Feldotte, 47, and her husband earned a combined $80,000. She considered herself solidly middle class. The couple and their four children regularly vacationed at a lake near their home in Saginaw, Mich.
But in August 2012, Feldotte was laid off from her job as a special education teacher. She's since managed to find only part-time teaching work. Though her husband still works as a truck salesman, their income has sunk by more than half to $36,000.
"Now we're on the upper end of lower class," Feldotte said.
Americans' self-perception coincides with data documenting a shrinking middle class: The percentage of households with income within 50 percent of the median—one way to define a broad middle class—fell from 50 percent in 1970 to 42 percent in 2010.
The Pew survey didn't ask respondents to specify their income. Still, Pew has found in the past that people who call themselves middle class generally fit the broad definitions that economists use.
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Roughly 8.4 percent of respondents to the National Opinion Research Center's survey, last conducted in 2012, said they consider themselves lower class. That's the survey's highest percentage ever, up from 5.4 percent in 2006. NORC is a social science research organization at the University of Chicago.
Tom Smith, director of the NORC, said even slight shifts are significant. Class self-identification "is traditionally one of the most stable measures" in the survey, he said.
By contrast to the most recent recession, the severe 1981-82 downturn had little effect on class self-identification in Smith's survey.
Why do so many no longer regard themselves as middle class? A key reason is that the recession eliminated 8.7 million jobs. A disproportionate number were middle-income positions. Those losses left what economists describe as a "hollowed out" workforce, with more higher- and lower-paying and fewer middle-income jobs.
Rob McGahen, 30, hasn't yet found a job that paid as well as the purchasing agent position at Boeing's defense division that he left in 2011. Nervous about the sustainability of that job because of government defense cuts, McGahen quit after buying a bar near his St. Louis home.
The bar eventually went bankrupt and cost him his house. He and his wife moved to Pensacola, Fla., where he's had little luck finding work in defense contracting.
Now, he works in the produce section of a supermarket. His wife earns the bulk of their income as a speech pathologist. Their household income has been cut in half, from $110,000 to $55,000, and he and his wife have put off having children.
"It's definitely been a step back," McGahen said.