ON JANUARY 22nd KFC announced that its Japanese stores faced a shortage of potatoes. McDonald’s, too, rationed fries in Japan in December, despite an “emergency” airlift of nearly 1,000 tonnes of spuds. The cause in both cases: massive delays at America’s West Coast ports.

Cargo is piling up inside the terminals. Exporters and importers are bleeding cash. The North American Meat Institute says delays are costing meat and poultry producers $30m a week. Chelan Fresh Marketing, a Washington fruit supplier, has laid off a fifth of its workforce. It is “a huge mess,” says Jon Wyss, Chelan’s head of government affairs.

The Pacific Maritime Association (PMA), which represents port operators, is battling the International Longshoremen and Warehouse Union (ILWU). The two groups have worked without a contract since July. The PMA says the union is co-ordinating a slowdown. By limiting the availability of skilled workers such as crane operators, the union has quietly created a bottleneck. “It’s like putting a football team of 11 guys out on the field, but not one of them is a quarterback,” says a spokesman for the PMA. The union denies it, arguing that the bottleneck is caused by larger ships and a near-record volume of goods.

If workers formally go on strike, they lose their wages. An informal go-slow imposes no such hardship. Hence its appeal, especially at a time when unions are losing their clout. Back in 1953, 36% of American private-sector workers were unionised; now only 6.6% are. Unions that remain strong typically represent workers doing essential jobs that are hard to outsource, says Tom Juravich, a professor of labour studies at the University of Massachusetts, Amherst. Transport workers are often unionised; shop workers typically are not.

The dockers are not angry about wages—which are relatively high for blue-collar workers at $25-$35 an hour—but about outsourcing. They want shippers and terminal operators to stop hiring non-union labour to maintain and repair the chassis, or truck beds, that carry cargo from dockside yards to warehouses. On January 26th the two sides reportedly reached a tentative agreement on this issue, but it may take weeks or months until they formally approve a new contract—and the ports run properly again.

Meanwhile, frustrated exporters and importers will find other routes. In a recent survey by the Journal of Commerce, 60% of shippers said they had begun redirecting cargoes away from America’s West Coast ports. Once that business leaves, it may never return. Western ports have already lost market share to the East Coast since 2002, when failed labour talks led to an 11-day lockout and a total shutdown.

More ominously, the Panama Canal is being widened to accommodate larger ships. That task will soon be completed, allowing ships from Asia to bypass the West Coast entirely and deliver goods directly to the Eastern seaboard. Jacksonville, Florida opened a new container terminal in 2009; traffic from Asia is already booming, even before the new-look Panama canal opens.

“We refuse to be held hostage forever,” says Shelly Boshart Davis, vice-president of a straw exporter in Oregon that uses West Coast ports to ship its hay to hungry cows in South Korea and Japan. She is considering exporting via Vancouver instead. “We will do whatever is necessary to keep our customers,” she says.