In this country, all children are supposed to have a shot at success — a chance to jump "from rags to riches" in one generation.
Even if riches remain out of reach, then the belief has been that every hard-working American should be able to go from poverty to the middle class.
On Tuesday, a book and a separate study are being released — both turning up evidence that the one-generation leap is getting harder to accomplish in an economy so tied to education, technological know-how and networking.
Harvard political scientist Robert Putnam's new book, Our Kids: The American Dream in Crisis, argues that the United States is losing its status as a land of opportunity for all.
Here's the central idea: In the American Dream, upward mobility is available to all, limited only by ability and effort, not class. But Putnam assembles data to show that an "opportunity gap" has emerged here, making an upward climb much tougher in the 21st century, compared with the mid-20th century.