What is also striking about the data is that the poor today are, in general, not the same people who were poor even a few years ago. For example, the new Census data find that only 3% of Americans are “chronically” poor, which the Census Bureau defines as being in poverty for three years or more. Many of the people in the bottom quintile of income earners in any one year are new entrants to the labor force or those who are leaving the labor force. Obviously, there is also a significant core of truly poor people in this group, but that core is drastically less than 100%.
“Alan Blinder of Princeton emphasized this point in a 1980 study: “The richest fifth of families supplied over 30% of the total weeks worked in the economy,” he wrote, “while the poorest fifth supplied only 7.5%. Thus, on a per-week-of-work basis, the income ratio between rich and poor was only 2-to-1. This certainly does not seem like an unreasonable degree of inequality.”
“To repeat, there is no evidence that it has become harder to get ahead through hard work at school and on the job. Efforts to claim otherwise appear intended to make any gaps between rich and poor appear unfair, determined by chance of birth rather than personal effort. Such efforts require both a denial that progress has been widespread and an exaggeration of income differences.”
http://www.thefreemanonline.org/featured/income-mobility-alive-and-well/ (Income Mobility: Alive and Well by David Henderson)