I keep hearing this, but where is the evidence? Was there any objective research done to figure out whether at any point there was really some sort of magnificent economic mobility in the U.S.? There's lots of anecdotal evidence, sure -- stories of people who immigrated here with nothing and made it big, movies, novels, etc... but how do we know we're not just hearing about the exceptions, and that in the vast majority of cases, which do not capture people's imaginations, the poor stayed poor and the rich stayed rich?