American Trucking Associations’ advanced seasonally adjusted For-Hire Truck Tonnage Index increased 6.6% in all of 2018 – the largest annual gain since 1998 (10.1%) and significantly better than the 3.8% increase in 2017.

The annual gain was realized despite a decrease of 4.3% in December to 111.9, down from November’s level of 116.9.

“The good news is that 2018 was a banner year for truck tonnage, witnessing the largest annual increase we’ve seen in two decades,” said ATA Chief Economist Bob Costello. “With that said, there is evidence that the industry and economy is moderating as tonnage fell a combined total of 5.6% in October and November after hitting an all-time high in October.”

November’s change over the previous month was revised down to -1.3% (+0.4% was originally reported on December 18).

Compared with December 2017, the SA index increased 1.4%, the smallest year-over-year increase in 2018. In November, the index was 5.8% above the same month in 2017.

The non-seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 107.8 in December, which was 7.8% below the previous month (117). In calculating the index, 100 represents 2015.

Trucking serves as a barometer of the U.S. economy, representing 70.2% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 10.77 billion tons of freight in 2017. Motor carriers collected $700.1 billion, or 79.3% 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.