"The immediate priority is damage control, as the reciprocal tariffs are already in effect, with no time allowed for a smooth transition."

— Zahid Hussain, ex- lead economist of World Bank's Dhaka office.

As US President Donald Trump yesterday unfurled his list of tariffs targeting most of America's trading partners, he repeatedly stressed that each nation's rate was reciprocal.

But he said little about the methodology behind those calculations.

A possible answer emerged later. Each country's new tariff rate appeared to have been derived by taking America's trade deficit with that nation and dividing it by the US imports from that country. Then, the percentage number was cut in half.

For Bangladesh, this meant dividing the US trade deficit of $6.2 billion by the total purchases from Bangladesh ($8.4 billion). That comes to about 74 percent. The calculated figure was then halved to 37 percent, the "discounted reciprocal tariff".

"The consequences [of US tariffs] will be dire for millions of people around the globe."

— Ursula von der Leyen president of the European Commission

Trump previously said each nation's tariff rate would be "the combined rate of all their tariffs, non-monetary barriers and other forms of cheating".

Those non-monetary barriers include a host of hard-to-quantify laws and other policies that Trump sees as the primary reason that the US experiences such trade imbalances in the first place.

There are exceptions: some nations, including the UK, face only a standard 10 percent minimum tariff starting this month.

In an earlier briefing with reporters, White House officials said the figures were calculated by the Council of Economic Advisers using well-established methodologies. The model was based on the concept that the trade deficit that the US has with any given country is the sum of all the unfair trade practices and "cheating" that country has done.

"The legitimacy of this tariff -- whether reciprocal or punitive -- depends on the accuracy of the US Trade Representative's calculations. This method's arbitrariness is difficult to comprehend," said Zahid Hussain, a former lead economist at the World Bank's Dhaka office.