People fall in and out of the categories all the time due to job loss or raises or selling a bunch of stock to make the down payment on a house. Some people ar

People fall in and out of the categories all the time due to job loss or raises or selling a bunch of stock to make the down payment on a house. Some people are stuck in the lower quintiles, and some people "stuck" in the higher ones. Other people float around or jump due to life events.