The number of heavy-duty truck drivers in 2011 rose 2.8% to 1.51 million from 1.46 million in 2010. It's the first yearly increase in the number of heavy truck drivers since 2008, when the number was 1.67 million, according to the Bureau of Labor Statistics.

Mean hourly wage increased last year to $19.15 per hour for heavy-duty truck drivers from $18.97 in 2010, and mean annual wage increased in 2011 to $39,830 from $39,450.

Since the beginning of 2012, the industry has added about 9,800 jobs. From February to March, however, there was a drop of 1,900 jobs, according to BLS. That was the first decrease since August 2011. Despite the drop, the American Trucking Associations pointed out in its weekly economic newsletter, during the first quarter, trucking payrolls increased 14,400.

For March 2012, the country's overall unemployment rate is 8.2%, little changed from last month but up from last year's March unemployment rate of 9.7%. Payroll employment for the entire U.S. was up 120,000 from February to March.

ATA Chief Economist Bob Costello points out even though overall job creation was lower than expected in March, manufacturing payrolls continue to increase, rising another 37,000 after 31,000 in February. Manufacturing is a key source of truck freight.