This is interesting.
Most of the statistics I see about such things measure which majors or degrees earn the most on average.
But the Washington Post reports a survey from PayScale that asks a slightly different question.
Mathematics is 10th on the "least underemployed majors" list. With a mathematics degree you can do many things!
I am surprised that the very least underemployed is civil and environmental engineering. But not too surprised. I have a brother-in-law who does civil structural engineering who gets job offers all the time.