Calling the end of the global trading system, or at least of sustained expansion in cross-border commerce, is now a tradition that stretches back two decades. The bursting of the 1990s tech bubble; the September 11 attacks; an international epidemic of avian flu in 2005. All were predicted to throw sand in the wheels of globalisation, and all failed to do so.
Even the global financial crisis, with its echoes of the Great Depression, did not bring the system crashing down, although it caused a huge drop in world goods trade. True, the growth of goods trade since the world economy recovered has been markedly lower relative to overall gross domestic product than it was over the previous decade. Still, it has continued.
US president Donald Trump is the biggest threat to the benign if fragile situation since the global crisis. It is not just the steel and aluminium tariffs that he has imposed on a series of trading partners, nor the much more expansive duties on imports from China, but the sense that businesses can no longer rely on the US as an anchor to the world trading system. Multinational companies are reassessing their cross-border supply chains with a renewed focus on political risk.
Happily, the threat to trade remains largely potential rather than actual. The most recent figures, part of the regular data series published by the Dutch Bureau for Economic Policy Analysis, showed the global volume of trade in goods recovering in August after a blip earlier in the year. The annual rate is heading back up towards a healthy 4 per cent, higher than over most of the past five years.
Whether this will continue is uncertain. The latest data are for August, before the impact of Mr Trump’s later tariffs on China had time to take full effect. Forward-looking indicators such as the effect of the international trade environment on capital spending plans have been weak, though not strikingly so.
However, as the OECD argued this week, if Mr Trump goes ahead with his threat to impose 25 per cent across-the-board tariffs on imports from China, let alone on other trading partners, the impact is likely to be much more dramatic.
In the face of this threat to trade and the global economy, there is, realistically, a limited amount that international co-operation can achieve. The G20 meeting in Buenos Aires next week is unlikely to provide much counterweight.
The grouping has repeatedly condemned protectionism in general terms over the past ten years, but rarely has any member country seemed to regard that as a binding constraint. This time round, the subject has proved so contentious that the draft communique omits even the usual rhetorical pledge to avoid raising new trade barriers.
The big trading economies, such as the EU and Japan, need to ensure they do not get dragged into tit-for-tat tariff increases themselves. And if the global economy slows, whether as a result of a trade war or because the long expansion has run out of steam, both monetary and fiscal policymakers should stand ready to offset the weakness with more stimulus.
The probability that this will be explicitly co-ordinated, at least on the fiscal side, is low. The US is no more likely to allow its tax and spending to be determined by international agreement than its tariffs.
The global economy is currently in a state of eerie calm. A trade war is raging, but economic output has yet to be caught in the crossfire. It would be foolhardy to assume that growth and trade will remain immune for too long.