The latest drop put the seasonally adjusted index at 114.4 (2000=100) in August, down from the July level of 114.6. July's decrease was less than the preliminary 1.3% ATA reported on Aug. 23.
Compared with August 2010, seasonally adjusted tonnage was up a solid 5.2%. In July, the tonnage index was 4.5% above a year earlier.
The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 123.8 in August, which was 10.9% above the previous month.
"Freight has been going sideways for much of this year, but it isn't falling significantly either, which suggests the U.S. economy just might skirt another recession," ATA Chief Economist Bob Costello said.
Anecdotally, Costello noted carriers are handling as much freight as they can.
"In part, this is due to less industry supply. The number of trucks operated by the truckload industry is still down about 12% from the height in late 2006, yet tonnage levels are about the same as in late 2006," Costello said. "Additionally, most carriers are finding it very difficult to hire new truck drivers, which mean they can't add too many trucks."
Each month, ATA asks its membership the amount of tonnage each carrier hauled, including all types of freight. The indexes are calculated based on those responses. The sample includes an array of trucking companies, ranging from small fleets to multi-billion dollar carriers.