[JPhillips]

You're ignoring the fact that people age. As you get older, you generally get more money and move up the income ladder. You aren't kicking someone out of your new bracket, people die, people are born. The problem in the US is that that movement isn't happening as much as in the past. Wealth is being concentrated in the hands of fewer families and their children start rich and end rich. The movement over time isn't happening.