The American Trucking Associations’ advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index rose 3.3% in October, following a 1.9% decline during September. In October, the index equaled 147.6 (2000=100), up from 142.9 in September.

Compared with October 2016, the SA index surged 9.9%, which was the largest year-over-year increase since December 2013. In September, the index increased 6.3% on a year-over-year basis. Year-to-date, compared with the same ten months in 2016, the index is up 3.1%.

ATA also revised its September decline in the index down to a 1.9% drop from the previously reported 0.9% decrease.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 151 in October, which was 5.1% above the previous month (143.7).

“Continued improvement in truck tonnage reflects a much stronger freight market,” said ATA Chief Economist Bob Costello. “This strength is the result of several factors, including consumption, factory output, construction and improved inventory levels throughout the supply chain. Additionally, the 6.7% rise in tonnage over the last four months suggests to me that retailers are expecting a good holiday spending season.”

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.