Piketty's Inequality Theory Gets Dinged

The 19th century is especially interesting because it's one of the few points in history where it benefited the rich to grant purchasing power to the non-rich.

In other words, the industrial revolution can't happen unless there is a broad base of consumers driving demand.

So to the prediction that "the rich get richer until a big war or revolution resets things", you might be able to add, "or the rich decide that they can secure future riches by sharing present-day riches".

In effect, they are investing in the growth of a strong consumer class to cement the demand for the widgets their factories produce.