Truck tonnage has flattened out, according to the American Trucking Associations, which has seen its tonnage Index falling slightly for the past two months in a row.

ATA’s advanced seasonally adjusted For-Hire Truck Tonnage Index dropped 1.5% in June after falling 1% in May. In June, the index equaled 111.6 (2015=100) compared with 113.3 in May.

“Tonnage has definitely flattened out, on average, over the last six to nine months,” said ATA Chief Economist Bob Costello. “The good news is that it remains slightly above 2020 levels."

Compared with June 2020, the seasonally adjusted index rose 0.5%, which was preceded by a 3.3% year-over-year increase in May. Year-to-date, compared with the same six months in 2020, tonnage is up 0.3%.

“Supply chain issues are likely putting some downward pressure on tonnage,” Costello said. “But it is also likely that tonnage isn’t growing as much as it could because of industry-specific supply constraints. This index is dominated by contract freight, and the for-hire truckload carriers have seen their tractor counts fall because they are having difficulty finding qualified drivers. It is difficult to move more tonnage with less equipment, which is why we are seeing strong volumes in the spot market as shippers scramble to get loads moved.”

May’s reading was revised down slightly to -1% from ATA’s June 22 press release.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 116.2 in June, 2.4% above the May level (113.4).

In calculating the index, 100 represents 2015. ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. This is a preliminary figure and subject to change in the final report.