&gt;Seventy per cent of people born into the bottom quintile of income distribution never make it into the middle class, and fewer than ten per cent get into the top quintile. Forty per cent are still poor as adults.<p>I&#x27;m unconvinced this is a terribly concerning level of mobility. Some people seem to assume an ideal level of mobility would demonstrate no advantage to those born in upper quintiles (i.e., your birth quintile plays no role in your adult quintile), but given what we know about the importance of genetics in passing along favourable human capital characteristics, matching behavior in mating markets, and the importance of social capital -- it seems very reasonable that we would see less than &quot;perfect&quot; mobility.