The renminbi exchange rate has a new symbolic number for traders to obsess over. For nearly a decade before 2005, the figure implanted in investors’ minds was 8.28, the level at which Beijing targeted its currency against the dollar. Pleas, enticements and threats from the US to let it rise were finally rewarded in 2005 when China let the currency appreciate. After repegging it during the financial crisis in 2008-10 Beijing has since broadly followed a policy of managing the currency’s movements to prevent instability.

Recently, the renminbi has been hovering around a symbolic level of 7 to the dollar — round numbers often enjoy undue attention in the foreign exchange markets — and threatening to fall through it. That would mark the currency’s weakest point since 2008.

Official US protests against Chinese manipulation have risen in volume again under Donald Trump’s administration. These days, though, they make little sense. During the 2000s, the vast piles of foreign exchange reserves China was building up by selling renminbi for dollars, alongside a large and persistent current account surplus, suggested US complaints about manipulation were justified.