After a year of quarterly increases, the turnover rate for truck drivers at large truckload fleets unexpectedly dipped one percentage point to an annualized rate of 88%, according to American Trucking AssociationsChief Economist Bob Costello.

"This reprieve, while surprising, is likely temporary," says Costello. "As the economy continues to recover, freight volumes should continue to grow, which along with regulatory challenges related to hours-of-service and the government's CSA fleet oversight program, will continue to cause the driver market to tighten and the turnover rate to rise."

Turnover among large truckload fleets had risen to 89% in the third quarter of 2011 after bottoming out at 39% in the first quarter of 2010.

For all of 2011, the large truckload turnover rate averaged 83% - the highest average since 2007 when churn averaged 117%.

At small truckload firms, with less than $30 million in annual revenue, the turnover rate dipped to 55% from 57% in the previous quarter. The fourth quarter turnover rate for less-than-truckload fleets fell to just 7% from 10% in the third quarter.