The tragedy is that Trump’s program will only strengthen the trend towards inequality. - Thomas Piketty

How do wealth- and capital-output ratios evolve in the long run, and why? Until recently it was difficult to properly address this question, for one simple reason: national accounts were mostly about flows, not stocks. Economists had at their disposal a large body of historical series on flows of output, income and consumption – but limited data on stocks of assets and liabilities. When needed, for example for growth accounting exercises, estimates of capital stocks were typically obtained by cumulating past flows of saving and investment. This is fine for some purposes, but severely limits the set of questions one can ask.

The distribution of wealth is one of today’s most widely discussed and controversial issues. But what do we really know about its evolution over the long term? Do the dynamics of private capital accumulation inevitably lead to the concentration of wealth in ever fewer hands, as Karl Marx believed in the nineteenth century? Or do the balancing forces of growth, competition, and technological progress lead in later stages of development to reduced inequality and greater harmony among the classes, as Simon Kuznets thought in the twentieth century? What do we really know about how wealth and income have evolved since the eighteenth century, and what lessons can we derive from that knowledge for the century now under way?

Economists are all too often preoccupied with petty mathematical problems of interest only to themselves. This obsession with mathematics is an easy way of acquiring the appearance of scientificity without having to answer the far more complex questions posed by the world we live in.