When looking at quintiles through time, remember that you aren't tracking people through time. That's because people move through the quintiles over time (how m

When looking at quintiles through time, remember that you aren't tracking people through time. That's because people move through the quintiles over time (how much, I don't know, but the groups are not static). In other words, it could show simply a greater variance in income within individual lifetimes rather than a greater variance in income between people. For instance, if people spend more time at school, but their incomes a few years after graduation are much higher, that would appear as a quintile disparity because they spent years in the bottom quintile (college and just after graduation), and then jumped into one of the top quintiles. Similarly, as skills become more important, then (whether you go to college or not), you'll spend more time at low pay before your skill level matures, and then your income will rise rapidly. Also, income is not wealth. Upper-middle class and rich people often spend a lot of time in the bottom quintile (unless they are so rich that they have a lot of passive income). I'm not saying there isn't a problem. I don't have the data. But that particular measure is quite deceptive in my opinion.