Economists say levies of between 10% and 50% have dramatically added to the risk of a worldwide downturn

Global financial markets have been plunged into turmoil as Donald Trump’s escalating trade war knocked trillions of dollars off the value of the world’s biggest companies and heightened fears of a US recession.

As world leaders reacted to the US president’s “liberation day” tariff policies demolishing the international trading order, about $2.5tn (£1.9tn) was wiped off Wall Street and share prices in other financial centres across the globe.

‘Willing sycophants’ came up with simplistic formula that has thrown global economy into disarray

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Waving a big chart as a prop in the White House Rose Garden, Donald Trump suggested his new tariff plan was simple: “Reciprocal – that means they do it to us, and we do it to them. Very simple. Can’t get simpler than that.”

Perhaps a bit too simple. The method used to calculate the most important numbers in international trade, politics and economics has left some of the world’s leading experts shocked.

Goods trade deficit: $291.9bn

Total goods imports: $438.9bn

Those figures divided = 0.67, or 67%

And halved = 34%

Reciprocal tariffs are calculated as the tariff rate necessary to balance bilateral trade deficits between the US and each of our trading partners. This calculation assumes that persistent trade deficits are due to a combination of tariff and non-tariff factors that prevent trade from balancing.