It is scarcely a surprise to learn that all is not well in the world of global trade. Donald Trump has slapped tariffs on steel and aluminium imports from countries around the world in response to a bogus threat to national security. The US president has forcibly renegotiated the North American Free Trade Agreement, now renamed the US-Mexico-Canada Agreement, to make it harder to maintain cross-border supply chains, particularly for cars. His administration has threatened the EU with punitive duties on autos unless it comes to the table and negotiates access to its agricultural market. And most obviously, he has now hit about half of China’s exports to the US with tariffs and is threatening more to come.

Yet these extraordinary actions have only now started to show up in the trade data in any significant way. Steel and aluminium may be symbolic sectors, but they are relatively small ones. Only the China tariffs really cover a substantial amount of bilateral trade with a major US trading partner.

The effect of the tariff war is becoming apparent. Data released last Monday showed that both Chinese exports and imports fell in December, a much weaker out-turn than economists expected. But while the export figures partly reflected the effect of the US tariffs, sales to other countries were poor as well, and the fall in imports revealed weak domestic demand.