Because of hiring booms in the late 70's and early 80's there are a lot of retirements right now, especially with all the attacks on pension benefits. People who have reached that magic age are bailing out before they lose benefits.
I doubt there are a lot of people just quitting. Some agencies laid people off or had hiring freezes, but they are starting to hire again.
Your degree gets you a POST bonus with most departments, and allows you to earn your Intermediate POST certificate two years sooner than with an Associates Degree.
If You Heard The Shot, You Weren't The Target