I have to question the headline (and the underlying data).
First, it wouldn't surprise me if a reporter played a little loose with the truth to get the results they want. For example, do you count railroad workers if they transport coal? How do you count them if they spend 18% of their time transporting coal, and while doing so coal is 42% of the total cargo? AFAIK, they don't sell coal at Wallymart, but they do sell solar powered battery chargers -- does that mean everyone down to the greeter is part of the "solar industry"?
And then there's marketing and sales. Where I live, it's a coin flop if I even run the heat at all in a year. Never met anyone who wanted to sell me coal (maybe it's different in the NE?). But something is going on with solar lately. I can't answer my door, answer my phone, open a web page on my phone/tablet, or drive down the block without someone trying to convince me that I can get solar panels for no money up front.