American Trucking Associations' advanced seasonally adjusted For-Hire Truck Tonnage Index increased 0.1% in July, following a 4.4% drop during June. In July, the index equaled 138.5 (2000=100), up from 138.4 in June.

Compared with July 2016, the SA index increased 2.3%. In June, the index rose 1.2% on a year-over-year basis. Year-to-date, compared with the same seven months in 2016, the index is up 1.2%.

As part of this report, ATA also revised its June drop in the index downward to a 4.4% decrease from the previously reported 4.3% decline.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 141 in July, which was 2.2% below the previous month (144.2).

"July's small increase in truck tonnage fits with other mixed economic indicators," said ATA Chief Economist Bob Costello. "Retail sales surprised to the upside, but manufacturing production and housing starts were down, so combined those likely caused a rather flat month in July for truck tonnage.

"With better economic growth in the second half of 2017, expect truck tonnage to continue increasing at a moderate pace on a year-over-year basis," he said.

Trucking serves as a barometer of the U.S. economy, representing 70.6% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled nearly 10.5 billion tons of freight in 2016. Motor carriers collected $676.2 billion, or 79.8% 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.