The duties took effect at one minute past midnight on Saturday, after three days of talks in Washington ended without a deal. Fifty percent, on roughly twenty billion dollars of Canadian goods, with no expiry date attached and no exemption for products that comply with the continental trade agreement the two countries signed and ratified.

Twenty billion sounds enormous until you put it against the denominator. Canada sent the United States something like three hundred and seventy billion dollars in goods last year. The tariffed slice is a bit over five percent of that. Nobody’s economy turns on it.