I think it depends on how you cluster job categories. If you make a giant retail job category, then of course it will be the largest. From the article:

> The Bureau of Labor Statistics has a system, but it’s a bit arbitrary. The BLS classification system attempts to group together workers who have similar duties and skills, but it’s as much art as it is science.

> For instance, the BLS sorts 7 million teachers into more than 80 separate occupations. (Special-ed teachers in elementary schools have a different occupation than special-ed teachers in preschools, middle schools or high schools, for instance.) But all 4 million retail salespersons are lumped into one large category, whether they sell lumber or lingerie.

> That’s where NPR was led astray. NPR looked at a data set that aggregated various kinds of truck drivers into a single category but that didn’t aggregate other occupations in the same way. The sorting was inconsistent, so the comparison isn’t a legitimate one, and it makes us think that truck driving is the most common occupation in many states.

On some of these surveys, I've seen Computer Programmer come up as the most common job in my state, which is definitely not true :).