Gloomy commentators have always argued that scarce resources will halt economic growth and their prognostications have always been wrong. Human ingenuity has found new resources and substitutes for old ones – oil and gas replaced coal, the artificial fixation of nitrogen solved the scarcity of bird droppings for use as fertiliser, and plastics substituted for pretty much everything.

But economic growth in affluent societies does not mean an increased claim on resources because growth is now mostly about better stuff, not more stuff. Alan Greenspan, the former Federal Reserve chairman, has been reported as saying that America’s gross domestic product weighs no more than it did a century ago. It is hard to see how even the great sage could know this, but easy to see what he means. At the beginning of the 20th century big companies such as US Steel, Pullman and International Harvester made goods you could stand on or sit in. Their counterparts today are Microsoft, Pfizer and Coca-Cola, whose products fit in your pocket.