What is the career field that is least subject to changes?

I just read the part in David Simon's HOMICIDE: A Life on the Killing Streets where they couldn't find some guy's body because it had been tossed into a mass grave down by a creek at the edge of the cemetery and it reminded me of the Burr Oak Cemetery scandal in Alsip (IL) last year. People be gettin' disinterred, for real.

oops it's a YEAR on the killing streets
you know what i meant

Love that book.