The number of shipping containers carrying U.S. imports fell for a second straight month, a private gauge showed, putting the economic indicator on course for one of the sharpest year-on-year reversals on record as President Donald Trump’s tariffs disrupt purchases of goods from abroad.

Inbound container volume fell 7.9% in June from a year before, after a 6.6% drop in May, veteran industry analyst John McCown wrote in a monthly report on July 20 based on the 10 largest U.S. ports. The declines more than wiped out a nearly 10% increase tied to inventory front-loading in April, and left the second quarter down 1.8% from a year earlier.

“The downward turn in 2025 will be due to tariffs and unfortunately there is nothing at present that suggests it will be short-lived,” McCown wrote.

After a 15% gain last year, “it is now most likely that there will be a decline in overall annual inbound volume in 2025,” said McCown, whose mentor was Malcom McLean, the North Carolina trucking executive who pioneered containerization in the 1950s. “That will be one of the more striking year-to-year changes in U.S. container volume in the six-decade history of the shipping container.”

The volume weakness is reflected in spot rates for containers transported to the U.S. West Coast from China, which have dropped for five straight weeks, according to Drewry, a maritime data and analytics company.

McCown said he was only aware of two periods of annual volume declines — during the global financial crisis and the pandemic — and both were short-term slumps.

He estimated that a 25% reduction in US container volumes is “readily possible” and would translate “directly into a $510 billion reduction in annual commerce for the U.S.” The total value of goods in containers moving through U.S. ports last year was $2.2 trillion, according to McCown’s data.