rom the Washington Post:

Many in U.S. slip from middle class, study finds 

By Michael A. Fletcher, 

Nearly one in three Americans who grew up middle-class has slipped down the income ladder as an adult, according to a new report by the Pew Charitable Trusts. 

Downward mobility is most common among middle-class people who are divorced or separated from their spouses, did not attend college, scored poorly on standardized tests, or used hard drugs, the report says. 

... The study focused on people who were middle-class teenagers in 1979 and who were between 39 and 44 years old in 2004 and 2006. It defines people as middle-class if they fall between the 30th and 70th percentiles in income distribution, which for a family of four is between $32,900 and $64,000 a year in 2010 dollars. 

People were deemed downwardly mobile if they fell below the 30th percentile in income, if their income rank was 20 or more percentiles below their parents’ rank, or if they earn at least 20 percent less than their parents. ... 

Overall, African American men have a particularly hard time clinging to middle-class status. Thirty-eight percent of black men who grew up middle-class are downwardly mobile, nearly double the rate of white men, the report says. Hispanic men are slightly more likely than white males to fall down the economic ladder, but the difference was not statistically significant.
Among African Americans and Hispanics, men are more likely to slip than women, although the reverse is true among whites. 

The racial gap in mobility has perplexed researchers at Pew since a 2007 report that said nearly half of African Americans born to middle-income parents in the late 1960s plunged into poverty or near-poverty as adults. That report underscored the feeble grip many African Americans had on middle-class life, prompting researchers to probe deeper, said Erin Currier, project manager of Pew’s Economic Mobility Project. 

The new report called the performance of blacks on a key standardized test a factor that accounts for virtually the entire mobility gap separating the races. Black males scored much lower than white males on the Armed Forces Qualification Test, which measures reading comprehension, vocabulary and math ability. 

“Taking into account differences in AFQT scores between middle-class white and black men reduces the gap until it is statistically indistinguishable from zero,” the report said. 

The findings in the report are drawn from the National Longitudinal Survey of Youth, a group of 12,000 interviews that researchers have followed since 1979.