For the poor, 2015 was only slightly less impressive. The 10th and 20th percentiles posted their second-highest growth numbers. The only other year when income grew faster was 1968.

In fact, maybe things are getting as good as they used to be. The pattern of 2015 is similar to that seen in 1968: high-income growth among the middle class and poor, and moderate income growth among the rich.

From the chart, you can see that in percentage terms, the poor tend to have wider ranges of growth and decline, reflecting the kind of financial instability that they face.