Upward social mobility is no longer giving people overall a better life, says the best expert on the field. As some move upward, others move down. But only a small fraction move very far in either direction.

Decades ago, the developed world was creating many additional well-paid jobs, so there was more mobility upward than downward. Nowadays, neither one is true.

Thus, to make a large number of people better off in the developed world requires massively deconcentrating wealth (for instance, more support for the poor, a Green New Deal, and Medicare for All) or massively eliminating waste (such as, a Green New Deal, and Medicare for All).