So... what is the lesson you want us to take away? It's true that individuals have varying amounts of success and move in and out of any given bracket all the time, but why is that important to what is clearly a demographic point?

On average, if you were poor in the 80's you're poorer now. Some of your poor cohort aren't as poor, and some have lifted themselves out of poverty entirely. Yet more of them are doing worse than they were.

That's bad, right? It's a problem you'd like to see fixed, yes? And it certainly is what the statistic means.