Truck drivers dominated an examination of Census Bureau data from 1978 to 2014 by National Public Radio's Planet Money on the most popular jobs in the U.S., as the profession ranked as the most commonly reported occupation in 29 of the 50 states.

Click here to see the complete study on NPR.org.

So why is the profession of moving goods around the U.S. in such a demand?

The truck driving profession has managed to avoid two of the biggest trends affecting the job market: automation and globalization. Machines can't drive cars completely yet, though that could change by 2020 if companies like Mercedes-Benz and Google get their way. Companies also can't get someone in China to drive a truck in New York, which makes outsourcing jobs a little difficult.

Right now companies need hard working people to deliver goods to specific places in a timely fashion to satisfy their customers.

The field also benefited from the way the government categorizes jobs. It combines together delivery people and truck drivers into one large category. Other categories are split up more finely, like primary school teachers and secondary school teachers are split into separate categories.

"We used data from the Census Bureau, which has two catch-all categories: 'managers not elsewhere classified' and 'salespersons not elsewhere classified,'" said NPR about the survey. "Because those categories are broad and vague to the point of meaninglessness, we excluded them from our map."

There is also a huge demand for new drivers. Retiring truck drivers aren't being replaced quickly enough, and the industry needs more than 239,000 people behind the wheel of trucks by 2022.

The Planet Money study also revealed other interesting trends like the rise and fall of secretaries as a major job. Manufacturing jobs have also disappeared due to a combination of technological and globalization changes.

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