Sixteen years ago American stockmarkets reached their modern nadir. During the early 2000s European and emerging-market equities went on a bull run. By March 2008 America had entered recession and its financial crisis was under way. The country’s stocks accounted for less than 40% of the world’s total stockmarket capitalisation.

Fast-forward to today and things look rather different. America’s share of the world’s stockmarket capitalisation has climbed pretty consistently over the past decade and a half, and sharply this year. It now stands at 61%. That is astonishing dominance for a country which accounts for just over a quarter of global GDP. The extent of market concentration is all the more extreme given what is happening within the American stockmarket itself. Just three companies—Apple, Microsoft and Nvidia—make up a tenth of the market value of global stocks.