Yes, the single biggest factor is age. You want a net-worth distribution where the wealthiest people are at retirement age because they're going to quit working and then that wealth will be spent in their retirement. It's like a roller coaster, you want to be moving the fastest right before you enter the loop so that you can be sure not to stall right when you're upside down (or embarrassingly fail to make it even that far and end up rolling backwards.) If everyone was going the same speed all the time, we'd just have boring flat tracks and there would be no point in going on the ride.
