Truck tonnage slumped on a monthly basis in August, but still managed to post a 4.1% rise compared to the same month last year, the American Trucking Associations (ATA) said Tuesday.

The ATA's advanced, seasonally adjusted, For-Hire Truck Tonnage Index declined 3.2% in August after jumping 6.2% in July, the Arlington, Virginia-based group said. The ATA constructs its index based on a benchmark value of 100 for 2015 conditions, and said the figure equaled 118.3 in August, compared with 122.2 in July.

Despite that stumble, the seasonally adjusted index increased 4.1% over its level in August 2018, showing that it is "unlikely" the U.S. economy is entering a recession, the ATA said.

The conclusion is significant because trucking serves as a barometer of the overall U.S. economy, representing 70.2% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods, according to the ATA.

"The large swings continued in August, but the good news is the trend line is still up," ATA Chief Economist Bob Costello said in a release. "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."

"The large swings continued in August, but the good news is the trend line is still up. While there is concern over economic growth, truck tonnage shows that it is unlikely that the economy is slipping into a recession." - @ATAEconBob

— American Trucking (@TRUCKINGdotORG) September 24, 2019