Future historians will look back on the current decade as a turning point comparable with that of the Seventies. No, not the 1970s. This is not going to be another piece pointing out the coincidence of an unpopular Republican president, soaring oil prices, a sagging dollar and an unwinnable faraway war. I am talking about the 1870s.

At first sight, the resemblances across 130 years may not seem obvious. The 1870s were a time when conservative leaders such as Benjamin Disraeli, British prime minister, were powerful and popular. It was a time of falling commodity prices, after the financial crash of 1873 and the opening up of the American plains to agriculture. And it was an era of currency stability, as one country after another followed the British lead by pegging to gold.