American Trucking Associations' advanced seasonally adjusted For-Hire Truck Tonnage Index decreased 1.8% in August after increasing 1.9% in July. In August, the index equaled 112.9 (2015=100), down from 115 in July.

July's final index was unrevised from our press release on August 21, 2018.

Compared with August 2017, the SA index rose 4.5%, down from July's 8.6% year-over-year increase. Year-to-date, compared with the same period last year, tonnage increased 7.6%, far outpacing the annual gain of 3.8% in 2017.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 120.4 in August, which was 5% above the previous month (114.6).

"Truck freight remained solid in August despite the monthly decline," said ATA Chief Economist Bob Costello. "However, the year-over-year increase was the smallest since July 2017. The deceleration in the year-over-year increases has begun due to more difficult year-over-year comparisons. It was a year ago when freight began to surge. We should all expect smaller year-over-year gains going forward than we witnessed over the last year."

Trucking serves as a barometer of the U.S. economy, representing 70.2% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 10.77 billion tons of freight in 2017. Motor carriers collected $700.1 billion, or 79.3% 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 10th day of the month. The report includes month-to-month and year-over-year results, relevant economic comparisons and key financial indicators.