Rien ne peut être dit politesse

If we're going to pay polite attention to a French economist, we'd prefer one who has a clue, not these two political hacks;

Wealth inequality, it turns out, has followed a spectacular U-shaped evolution over the past 100 years. From the Great Depression in the 1930s through the late 1970s there was a substantial democratisation of wealth.

That word--our bold--doesn't mean what you think it means, Messieurs. Unless the French use it as a synonym for destruction. Since you seem to believe that the glory years for wealth were at the trough of the Great Depression through WWII, when the wealthy were put in their places. But, do you even bother to think about what you write;

The growing indebtedness of most Americans is the main reason behind the erosion of the wealth share of the bottom 90% of families. 

That's a choice. Not something imposed upon them from above by the evil rich. Not that the plebians weren't encouraged to borrow for consumption by the federal government. But that's another story (and one we've written copiously about, before). Again, as the two Frenchmen say;

How can we explain the growing disparity in American wealth? The answer is that the combination of higher income inequality alongside a growing disparity in the ability to save for most Americans is fuelling the explosion in wealth inequality.

So, the answer is to teach Americans to fish (and save those fish), rather than to give them fish? That seems not to have occurred to the boys from Berkeley and LSE.