This study deleted USPS employees. At the same time he is comparing a workforce with an average of a bachelor's degree, and a quarter with a master's degree against the average US workforce ~ hardly a fair comparison.
Just to make your day:
I joined the federal government in 2000, at age 61. I then paid abount $350 to get retirement credit for 4 years Military Academy time. A year later I was eligible to retire - for the third time. Private industry sure didn't offer that plan!