The persistent problem of churn among commercial truck drivers has spread to the smaller fry.

Driver turnover in 2014 among smaller truckload carriers—those with $30 million or less in annual revenue—spiked to 90 percent, an 11-point leap from 2013 levels, according to data released yesterday by the American Trucking Associations (ATA). The turnover rate among large carriers hit 95 percent in 2014, ATA said. The 5-point gap is the narrowest since 2000, the trucking trade group said.

In the fourth quarter, the driver churn rate among large truckload carriers hit 96 percent, while the rate for smaller carriers hit 95 percent, ATA said.

ATA chief economist Bob Costello said the narrowing turnover gap between large and small carriers is likely due to pay raises and bonuses offered by bigger carriers that are luring drivers away from smaller fleets. For example, C.R. England Inc., one of the largest haulers of refrigerated commodities, announced in late March an average pay increase of 26 percent for many company team drivers in its national and western regional divisions. That is Salt Lake City-based England's third driver compensation hike just in 2015.

Costello said the ongoing driver shortage—estimated by the group at between 35,000 and 40,00 drivers—remains "very high," and is becoming "more pervasive," at least in the truckload sector.

By contrast, turnover in the less-than-truckload sector, which represents a fraction of the revenue generated by the truckload business, stood at 11 percent, unchanged from the year before, ATA said. LTL drivers are generally better paid and have a more favorable work-life balance because they drive over relatively short hauls and as a result are able to get home more frequently. Improvements in LTL tonnage, yields, and profits may also be keeping more drivers in their current seats.