But there are other ways to discourage imports: wildcat strikes in the UK aimed a keeping British jobs for the British; governments' attempts to deter companies that have received public capital from investing outside their home country; exchange rate moves that revive talk of manipulation; and complaints that the scale of borrowing by the US will crowd out efforts by other governments to do so. All reflect ways of “protecting” local economies at the expense of global trade.

These developments imply that the world might yet slip into the beggar-thy-neighbour trade policies of the 1930s even without adopting the explicit tariffs. They help explain why equities are selling off once more.

If there was a return to economic nationalism, its effect would be to ensure almost unified and universal market falls. The S&P 500 had its worst January on record, down 8.6 per cent. Other developed indices did slightly worse, with the MSCI World index excluding the US down 9.3 per cent. There was little refuge in emerging markets, down 6.5 per cent, though big exporters China and Brazil saw bounces.