Trucks hauled more than 70 percent of freight tonnage in the U.S. last year, generating $676 billion in revenues, according to the American Trucking Associations. But the industry is grappling with a growing problem — a shortage of qualified drivers, as its current workforce ages and the labor market continues to tighten. Some 500,000 nonlocal, for-hire truckers are delivering freight in the U.S., and the industry needs 51,000 more, experts say. "We have more freight than we know what to do with, but in order to haul that freight, you've got to have more drivers — trucks don't drive themselves," said Bob Costello, the association's chief economist. "We have a couple of demographics problems in the industry — we have a high average age of the current truck drivers. We need to do a better job to get females in as truck drivers. The supply side is tight as well." The crunch is being felt in industries from construction to retail as the labor shortage's ripple effect grows. C.R. England, a Salt Lake City-based trucking company, works with big companies like Nestle and Walmart and employs some 6,500 drivers, but Chairman Dan England said it could use 500 more. "It's frustrating for us not to be able to meet the goals we have set in terms of growth. … We do have to disappoint customers on a regular basis. Every day we have many loads that are called in, and we just can't answer the calls and put a truck there," said England, whose company has been in his family for four generations. "We are interested in growing, the business is there. We just need the manpower and womanpower to get it done."

Driver demographics and the shortage

Costello says the average driver is 50 years old, and only 6 percent are women, making new drivers like Johnshell Jenkins a rarity. She's a 21-year-old Alabama native who just completed training with C.R. England and is ready to hit the road.

Dan England, chairman of his family’s fourth-generation company, C.R. England, says he could use 500 additional drivers to meet growing demand. Kate Rogers | CNBC

Benefits at the company include vision, dental and 401(k) retirement plans for drivers. Costello adds it's not uncommon to see pay raises once or twice a year for workers, and to have new drivers receive repayment for their school loans — something C.R. England offers its drivers after a year of service. "The benefits are great, the pay is great, and they offer a lot of miles," Jenkins said. "I like to travel and I like money so trucking is going to be best for me. I said, 'Just because this is a man's job, I can do the same thing as a man.' " One problem in attracting young workers to the industry is a federal law that mandates drivers must be at least 21 in order to ship interstate freight, meaning younger job candidates may pursue other career paths and never consider a career in trucking. "Those people aren't going to sit around and just wait to become a truck driver," Costello said. "They go fast food. They go to retail, maybe construction, and then they finally come to trucking, when they're like, 'You know what? I need a better paying job with good benefits.'" Trucking companies including Saia, Titanium Transportation, ArcBest and Ryder System have all noted wage increases for drivers on recent earnings calls as the shortage worsens. Titanium executives also noted the difficulty of finding millennials to drive for lower wages, forcing pay increases. Others are offering signing bonuses, flexible schedules and loan repayments for training to attract and retain workers. "Drivers aren't going to get any younger, and we need to attract younger people into this industry, and you're not going to get millennials to drive trucks at this point in time at the same rate that you had the previous generation for the current wage," Titanium CEO Theodor Daniel said on the company's earnings call in July. The average pay is $40,000 to $50,000 a year for a new driver out of school and can reach up to $80,000 a year for experienced workers.

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