By Benjamin Fearnow

WASHINGTON (CBS WASHINGTON) — In the course of Obama’s presidency, people saying they are in the “lower classes” have risen from one-quarter to one-third of the adult population.

According to the Pew Research Center, Americans who say they are in the lower-middle or lower-class has risen from 25 percent to 32 percent in the past four years, in the national survey of 2,508 adults.

Not only has the lower class grown, but its demographic profile also has shifted. People younger than 30 are disproportionately swelling the ranks of the self-defined lower classes. The shares of Hispanics and whites who place themselves in the lower class also are growing.

Among blacks, the story is different.

The share of blacks in the lower class has not changed in four years, one of the few demographic groups in which the proportion in the lower classes did not grow. As a consequence, a virtually identical share of blacks (33%) and whites (31%) now say they are in the lower class.

When it comes to political affiliation, more Democrats than Republicans place themselves in the lower classes, but those of the GOP saw a sharper rise over the past four years. Some 23 percent now call themselves lower class, up from 13 percent in 2008. Among Democrats, 33 percent now call themselves lower class, compared with 29 percent in 2008.

The survey finds that hard times have been particularly hard on the lower class.

Eight-in-ten adults (84%) in the lower classes say they had to cut back spending in the past year because money was tight, compared with 62 percent who say they are middle class and 41 percent who say they are in the upper classes. Those in the lower classes also say they are less happy and less healthy, and the stress they report experiencing is more than other adults.

To measure social class, the Pew Research surveys in 2012 and 2008 asked respondents this question: “If you were asked to use one of these commonly used names for the social classes, which would you say you belong in: the upper class, upper-middle class, middle class, lower-middle class or lower class?”

Few respondents in either survey placed themselves in the “lower class” or “upper class” categories. So for this report “lower class” constitutes those who placed themselves in the lower or lower-middle class. Those who identified themselves as upper or upper-middle class are combined to form the “upper class” group.

Looking ahead, a bleak future is predicted by many.

Many in the lower class see their prospects dimming. About three-quarters (77%) say it’s harder now to get ahead than it was 10 years ago. Only half (51%) say that hard work brings success, a view expressed by overwhelming majorities of those in the middle (67%) and upper classes (71%).

According to Pew, while the expectation that each new generation will surpass their parents is a central tenet of the American Dream, those lower classes are significantly more likely than middle or upper-class adults to believe their children will have a worse standard of living than they do.