Whiler I agree with the thrust of your comment, your committing an error: the distribution of incomes isn't uniform across time/age. That is, the set of under 3

Whiler I agree with the thrust of your comment, your committing an error: the distribution of incomes isn't uniform across time/age. That is, the set of under 30 and under 40 household with 12k/ year is lower than 40%. If you look at not the median household at this moment, but the lifecycle of the median household from when it started to when, it probably couldn't save 10k/yr until recently. And the early years are the most important ones.