American Trucking Associations' advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index increased 2.4% in September after rising 0.3% in August. In September, the index equaled 112.9 (2015=100) compared with 110.2 in August.

"The drivers of truck freight, including retail, construction, and manufacturing, plus a surge in imports, are helping keep demand high for trucking services," he said.

August's reading was revised down slightly to 0.3% from our September 21press release.

Compared with September 2020, the SA index rose 1.7%, which was the first year-over-year gain since May. In August, the index was down 0.7% from a year earlier. Year-to-date, compared with the same nine months in 2020, tonnage is unchanged.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 113.2 in September, 1% below the August level (114.3). In calculating the index, 100 represents 2015. ATA's For-Hire Truck Tonnage Index is dominated by contract freight as opposed to spot market freight.

Trucking serves as a barometer of the U.S. economy, representing 72.5% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 11.84 billion tons of freight in 2019. Motor carriers collected $791.7 billion, or 80.4% of total revenue earned by all transport modes.

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 issued around the 5th day of each month. The report includes month-to-month and year-over-year results, relevant economic comparisons, and key financial indicators.