The annualized driver turnover rate at the largest trucking carriers in the country rose to the highest level in three years, according to an American Trucking Association report.

The report indicates that during the 3rd quarter of 2015, the turnover rate of truck drivers at carriers with more than $30 million in annual revenue rose 13 percentage points, up to 100%.

The same report also indicates that the turnover rate at smaller carriers dropped to just 68%, which is the lowest level since 2011.

This means that larger carriers are having more difficulty retaining drivers, while driver retention at smaller carriers is improving.

ATA Chief Economist Bob Costello commented on the findings. “The increase in the turnover rate at large carriers matches up with what we’ve been hearing anecdotally from fleets: that the market for drivers continues to be tight.”