Donald Trump dislikes trade deficits. His attempts to remedy them with tariffs caused stocks and bonds to plunge. On Wednesday, after he rowed back, markets soared again. This mayhem threatens to erode the appeal of US investments. Which could, perversely, help Trump get what he wants.

To a president wary of depending on other countries, last year’s $918bn US trade deficit is a menace. To economists, though, it’s also an artefact of maths. Money that flows out to buy imports is the inverse, on a net basis, of money coming in to acquire financial assets. In econo-speak, the current account and the capital account must balance.

When one moves, therefore, so does the other. If America buys more exports, foreigners have more dollars to deploy in US assets. Treasuries are a safe bet. Shares in companies such as Nvidia, Apple and Berkshire Hathaway have been a profitable one. Foreigners own $19tn of US stocks, according to Treasury data, twice the level of five years ago.