To calculate its ‘reciprocal tariffs’, the Trump administration has opted for a crude formula with no basis in trade theory. We are all going to pay the price.

Switzerland’s tariffs could be much lower. Bermuda’s could be way higher. And Australia could have no tariffs at all.

The White House’s new tariffs were pegged to amounts it said other countries impose on the U.S. In many cases, those amounts appear to match a basic formula: the size of a country's goods-trade ...