American Trucking Associations’ advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index decreased 6.1 percent in May after jumping 7 percent in April. In May, the index equaled 114 compared with 121.4 in April.

“As expected, tonnage corrected in May from the surprising surge in April,” said ATA Chief Economist Bob Costello. “The economy is still growing, but the recent volatility in truck tonnage fits with a broader economy that is showing more mixed signals. The good news is if you ignore recent highs and lows, tonnage appears to be leveling off, albeit at a high level.”

April’s reading was revised down compared with its May press release.

Compared with May 2018, the SA index increased 0.9 percent, the smallest year-over-year gain since April 2017.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 119.1 in May, 1.5 percent above April level (117.4). In calculating the index, 100 represents 2015.

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 fifth day of each month.