IN APRIL 1956 the world’s first container ship—the Ideal X—set sail from New Jersey. A year later in Seattle the world’s first commercially successful airliner, Boeing’s 707, made its maiden flight. Both developments slashed the cost of moving cargo and people. Boeing still makes half the world’s airliners. But America’s shipping fleet, 17% of the global total in 1960, accounts for just 0.4% today.

Blame a 1920 law known as the Jones Act, which decrees that trade between domestic ports be carried by American-flagged and -built ships, at least 75% owned and crewed by American citizens. After Hurricane Irma, a shortage of Jones-Act ships led President Donald Trump on September 28th to waive the rules for ten days to resupply Puerto Rico. This fuelled calls to repeal the law completely.

Like most forms of protectionism, the Jones Act hits consumers hard. A lack of foreign competition drives up the cost of coastal transport. Building a cargo ship in America can cost five times as much as in China or Korea, says Basil Karatzas, a shipping consultant. And the cost of operating an American-flagged and -crewed vessel is double that of foreign ones, reckons America’s Department of Transportation.

Inflated sea-freight rates push most cargo onto lorries, trains and aircraft, even though these are pricier and produce up to 145 times as many carbon emissions. So whereas 40% of Europe’s domestic freight goes by sea, just 2% does in America. Lacking overland routes, Alaska, Guam, Hawaii and Puerto Rico are hardest hit. Hawaiian cattle ranchers, for instance, regularly fly their animals to mainland America. A recent report by the Government Development Bank for Puerto Rico found that the Jones Act inflated transport costs for imports to twice the level of nearby islands.

Jones-Act shipowners retort that the rules are to help producers, not consumers. Rail firms lobbied for the 1920 law, out of fear that an excess of foreign ships from the first world war was flooding the market. National security was also cited. German submarine warfare, it was argued, showed the need for a merchant fleet built and crewed by Americans. But the law has virtually wiped out American shipping. Between 2000 and 2016 the fleet of private-sector Jones-Act ships fell from 193 to 91. Britain binned its Jones-Act equivalent in 1849. Its fleet today has over three times the tonnage of America’s. Marc Levinson, an economic historian (and former journalist at The Economist ) notes that the laws also made American container lines less able to compete on international routes. Drawn by profits at home they underinvested in their foreign operations, and fell behind their foreign rivals because they lacked the same scale.

Recognising the harm to their domestic fleets, countries from Australia to China are loosening the rules protecting their fleets. Not America. In January, the Obama administration tried to get rid of all exemptions to the Jones Act. Mr Trump overruled that decision in May, but has said any further waivers will be hard because of the influence in Congress of lobbyists from the sailors’ unions and shipowners. Yet deregulation is part of his platform. The Jones Act would be a good place to start.