The American Trucking Associations' advanced seasonally adjusted For-Hire Truck Tonnage Index fell 4% in January after surging 6.4% in December 2011. The latest contraction put the index at 119.4 (2000=100), down from December's record level of 124.4.

"Last month I said I was surprised by the size of the gain in December," says ATA Chief Economist Bob Costello. "Today, I'm not surprised that tonnage fell on a seasonally adjusted basis in January simply due to the fact that December was so strong," Costello notes that December's increase was the largest month-to-month gain since January 2005.

A drop in durable goods orders was likely partly to blame for the drop. Durable goods also fell in January. According to published reports, the drop was caused by businesses cutting spending on machinery and equipment after a tax break expired. Orders for long-lasting manufacturing goods dropped the most they had in three years.

Overall durable goods orders for January totaled $206.1 billion; orders are still 16% below their peak hit in December 2007.

ATA recently revised its seasonally adjusted index back five years as part of its annual revision. For all of 2011, tonnage rose 5.8%, slightly lower than the 5.9% previously reported, and matched 2010's gain of the same magnitude. The January 2012 index increased 3.6% from January 2011.

The not-seasonally-adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 112.1 in January, which was 3.5% below the previous month.

"I'm still optimistic about truck tonnage going forward," Costello says. "In fact, while many fleets said January was normal, they are also saying that February has been pretty good so far."