"...recent research shows that in the Nordic countries and in the United Kingdom, children born into a lower-income family have a greater chance than those in the United States of forming a substantially higher-income family by the time they're adults.
If you are born into a middle-class family in the United States, you have a roughly even chance of moving up or down the ladder by the time you are an adult. But the story for low-income Americans is quite different; going from rags to riches in a generation is rare. Instead, if you are born poor, you are likely to stay that way. Only 35 percent of children in a family in the bottom fifth of the income scale will achieve middle-class status or better by the time they are adults [middle class being defined here as an income of $50,000 a year for a family of three]; in contrast, 76 percent of children from the top fifth will be middle-class or higher as adults."
Sawhill and Haskins go on to qualify this picture by noting that the U.S. "is exceptional" in the opportunities it offers to immigrants, relative to other 'developed' countries. But the basic data on mobility should not come as a big surprise. It is, of course, possible, as the 35 percent figure given in the quotation suggests, to rise from a poor or working-class family into the ranks of the middle-class or the affluent, but it's not likely. It probably requires a combination of individual talent, work, and luck (with "luck" construed to include the traits that one is born with and the quality of parenting one receives, among other things).
Anyone who doubts that the reproduction of social class takes place in the U.S., and who wants to consult something livelier and more anecdotal than the abundant academic literature on the topic, can browse through, say, a 30th anniversary Class Report from an elite college or university and note where the alumni's children are going to college. Anecdotal? Sure. Probative of anything in a strict social-scientific sense? No. But nonetheless quite revealing.
P.s. Last year I noted a piece by William Deresiewicz which bears on this last point.