Every month, Zac Rogers, a professor at Colorado State University, publishes a survey of supply chain managers called the Logistics Managers' Index. He asks them how much they’re charging for shipping, and how much capacity they have on trucks, trains, and in warehouses. And a few months ago, he noticed something he’d never seen at this time of year.

“We saw in August, September, and then through the first half of October, that capacity was growing faster than price,” Rogers said.

Rogers said that’s unusual because this is peak season, as retailers try to stock up ahead of the holidays. Supply chain capacity is usually low, and prices are high. But this year, he said companies shipped a lot of stuff before the president’s tariffs kicked in.

“Most of the things that needed to be imported for the holiday season came in in the summer,” Rogers said. “And so, all these places had a lot of inventory sitting there, for three months, and during those three months, nothing was really moving.”

Other data show that supply chain activity has been slowing down in recent months. Imports in August were down 5% from the month before, according to trade data out this week from the Bureau of Economic Analysis. And a report from the logistics company Descartes found that imports stayed weak in September and October.

But even if companies already have the holiday goods they need, Rogers said it can be a worrying sign when transportation capacity grows faster than the price of transportation.

“Every time we’ve seen that happen for three, four months in a row, we’ve dipped into a freight recession,” Rogers said.

Freight recessions are times when the transportation sector gets smaller. Profits shrink, hiring slows down, and some transportation companies might go out of business.

The transportation sector has already been showing signs of stress, said Meagan Schoenberger, senior economist at KPMG.

“One of the biggest leading indicators for freight is trailer production, production of the trucks that transport goods,” Schoenberger said. “It is extremely low at the moment.”

Schoenberger said the freight sector’s been struggling for a while now — really, ever since the pandemic. And while consumer spending has been holding up this year, the freight sector could slow further.

“The biggest question we have moving forward is: once people start to run out of those inventories that they stocked up on, do they start to restock the shelves with the same products?” Schoenberger said. “Do they order less?”

Schoenberger said a freight recession isn’t the same thing as a recession-recession. But if businesses do end up ordering fewer goods, Schoenberger said that would be a red flag for the overall economy.

“We’ve actually never really seen a significant decline in goods spending outside of a recession,” Schoenberger said.

Companies have a few reasons to order fewer goods this coming year. Tom Goldsby, a professor of supply chain management at the University of Tennessee, Knoxville, said for one, companies don’t know how consumer spending will hold up, given how difficult it is to forecast anything right now.

“Rather than relying on inventory to provide that safety blanket, as so many organizations would as they would typically enter into a healthy sales period, they might take more of a wait-and-see approach,” Goldsby said.

Plus, ordering too many goods can be costly.

“And if we see the general economy cooling off, it’s going to be even more costly because it means you’re holding on to inventory for a longer period of time,” Goldsby said.

But the economy might also keep humming along. And in that case, low inventory levels could actually cause the freight sector to pick up steam. Zac Rogers at Colorado State University said retailers would end up bringing in more goods more often.

“Because the pressures of costs on inventory are so big, it could actually push freight into a more robust market, because you need a lot of transportation if you’re going to be turning things over quickly,” Rogers said.

And that could help bring the freight sector out of recession.