I'm a librarian and I married another librarian. Other good possibilities for me were truck drivers, paralegals, and middle school teachers.
That's what this chart by Bloomberg Business indicates. Adam Pearce and Dorothy Gambrell analyzed US Census data from the 2014 American Community Survey. They examined who married whom by profession and gender. You can find the interactive chart here. It's fun to play to with!
Of all professions, elementary school teachers were the most likely to marry within their profession. Software developers, dentists, musicians, and air traffic controllers also tend to keep their loving in-house.
-via Flowing Data