Wealth is increasingly concentrated in fewer and fewer hands. The gap between rich and poor is widening between and within countries all over the world, a trend that “menaces vigorous societies” says Will Hutton, the former editor-in-chief of the UK’s Observer newspaper. But such growing inequality does not come about by itself. “It is a proxy”, says Hutton, “for how effectively an elite has constructed institutions that extract value from the rest of society.”

Public-Private Partnerships are one such institution.

PPPs come…