The turnover rate for drivers in the truckload sector took a surprising dip in the fourth quarter, according to the American Trucking Associations' Trucking Activity Report, the likely result of a weakened economy and overall freight volumes.

Turnover at large truckload carriers dropped from an annualized rate of 104% in the third quarter to 90%, its lowest point since the first quarter of the year. For all of 2012, turnover averaged 98%, the highest since 2007 when the churn rate averaged 117%.

At smaller truckload fleets, the turnover rate dipped to 76% from 94% in the previous quarter. Small fleet turnover averaged 82% in 2012 - the highest since 2007's average of 90%.

"As freight volumes slid a bit at the end of 2012, we saw turnover follow suit," ATA Chief Economist Bob Costello said. "However, this is just a respite from the long-term trend and driver shortage storm that's coming when the freight economy accelerates; and  even then, these relaxed levels are still quite high relative to recent years."

Costello said as it stands now, the industry is still short between 20,000 and 25,000 drivers in the truckload sector - a figure that a healthier economy will only force to grow.

"Once we see steadier, more robust economic growth, we could see an industry that is short by as many as 239,000 drivers by 2022," Costello said. "Hard as it may to believe, we may someday soon look back on turnover rates of just 90% as the good old days as increased demand, an aging workforce and regulatory constraints combine to push the shortage higher."