[mhneu]

Views of how the 'rich' live are vitally important today, when wealth inequality is the central social issue of our time, impacting government, policy, wages, and consumer markets alike. (Piketty).

Class mobility is good, of course - it's been a central tenet of American values, even if it's been smaller than thought. But I'm not sure that mobility between the 0.1% and 0.01% is the key flow - mobility between the middle 50% and top 5% is probably what we should be caring about.