NYU Sociologist Dalton Conley is about to publish a new book detailing some findings on intergenerational mobility. The main conclusion:

...differences between families explain only 25 percent of the nation's income inequality; the remaining 75 percent is explained by differences between siblings. More typical of the United States than President Bush and his brother Jeb, the governor of Florida, he suggests, are the White House's previous tenant, Bill Clinton, and his half-brother, Roger, a college dropout, onetime cocaine dealer and failed musician. Or, for that matter, Jimmy Carter and his ne'er-do-well brother, Billy

(link via marginalrevolution.com)