LAS VEGAS. Calling his forecast “reasonably bullish,” economist Stu MacKay doesn’t believe fleets will add capacity this year, “but they are at the point where they do have to replace stuff.”

Speaking at the Heavy Duty Aftermarket Dialog, the president of MacKay & Assocs. forecast a 17% increase in retail truck sales this year, but only a 0.4% increase in the overall commercial vehicle population.

MacKay’s 2014 forecast calls for slow but steady growth in Class 8 utilization through 2018 as fleets have learned to move more freight with fewer vehicles. Compared to the pre-deregulation 1970s, fleets today use 73% fewer Class 6/7 trucks and 46% fewer Class 8 vehicles to move the same value of goods, he said. More recently, fleets have pushed their efficiency up nearly one-third for heavy-duty trucks and roughly 25% for medium-duty since the 1990s.

Turning to aftermarket parts, MacKay forecast “solid growth” of 3.3% this year and continued slow steady gains through 2018. Parts related to engines and power generation will see the most robust growth (7.2%) driven by the industry's adoption of more complex emissions and electronics systems, he said.

Overall, MacKay said, “fleets will buy more trucks and more parts in 2014.”