I also wondered about that for NC at first...I thought "something didn't go to Mexico/China/Bangladesh?
But the thing is "disproportional" so...
I don't know any book-binders in MN, I used one (once) for my masters thesis...but if popular in terms of raw number, I would think unemployed leftist taxpayer-sucking low-life would be number one (and yes I think they think that is a proper vocation!) or among the traditionally employed maybe bait shop clerk!
Perhaps WV is right...Obama all but ended coal...