Bug Girl has a must-read piece for anyone contemplating graduate school in the sciences:
NEVER get a PhD because you think it will improve your job prospects. PhDs are trained to do research in an academic setting, for the most part. And that is….not, frankly, where the majority of jobs are. You will be disappointed and frustrated if you think getting a PhD will make getting a job “easier.”
Pursue a PhD because you love science, or because you have a burning question about a topic that you want to investigate further.