Container costs from China and East Asia to the east coast of the United States have climbed over $20,000, compared with only $4,000 a year ago, according to data from freight-tracking firm, Freightos, as reported by The New York Times.

Knock on effects from these price rises include ships diverting from other routes to chase this more lucrative option. Boats have been backing up at US ports, and empty shipping containers aren’t making their way back to China fast enough, exacerbating shipping issues.

US Federal Reserve officials have said they expect the faster price gains to prove “transitory,” but have also been careful to stress that supply chains are a major source of lingering uncertainty, making it unclear how quickly prices might regulate.

“I’m less in that ‘transitory’ camp,” Phil Levy, the chief economist at Flexport, which tracks ocean shipments and helps importers plan so that their parts can get in by desired dates, told The New York Times. “And more in the ‘we have reason to be concerned’ camp.”

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