American Trucking Associations' advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index declined 3.2 percent in August after jumping 6.2 percent in July. In August, the index equaled 118.3 (2015=100) compared with 122.2 in July.

“The large swings continued in August, but the good news is the trend line is still up,” said ATA Chief Economist Bob Costello. “While there is concern over economic growth, truck tonnage shows that it is unlikely that the economy is slipping into a recession. It is important to note that ATA's tonnage data is dominated by contract freight, which is performing significantly better than the plunge in spot market freight this year.”

July's reading was revised down compared with its August press release.

Compared with August 2018, the SA index increased 4.1 percent. The index is up 4.3 percent year-to-date compared with the same period last year.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 125.1 in August, 2.2 percent above the July level (122.3). In calculating the index, 100 represents 2015.

Trucking serves as a barometer of the U.S. economy, representing 70.2 percent 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 percent 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.