Which helps explain why there were just 36,000 U.S. operators in 2010, down nearly two-thirds in 10 years.
A job that rose in the same period? Software engineer. They numbered 1.03 million in 2010, up nearly 40 percent.
AP researcher Judith Ausuebel in New York contributed to this story. You can reach Bernard Condon on Twitter at http://twitter.com/BernardFCondon