Over half (54.24%) of United States Postal Service (USPS) City Carrier Assistants (CCAs) do not last 1 year before quitting: http://postalnews.com/blog/2016/02/20/usps-non-career-turnover-rate-doubles-most-ccas-dont-last-a-year/

From my father's experience as a CCA and various testimonies from former employees online, harassment by USPS supervisors appears to be the main driver causing employees to quit. 

My father has been working as a CCA for the USPS for approximately 7 months. He has received constant harassment by supervisors, often through verbal abuse and destructive criticism. When he asks how he can improve what he is being criticized on, supervisors are unable to answer.

Here's where the story gets crazy. His primary supervisor "fired" him, taking away his badge and work materials, only to have him return to work once they discovered he could not be fired without warning. My father enlisted the help of the union to recover his paycheck during the time he was "fired" and could not show up to work. Now, the harassment has only become worse as his supervisors retaliate and attempt to fire him for good. They have gone to extreme lengths to find ways to write him up, including stalking him on his route to see if he makes any mistakes. I personally witnessed a USPS van following his mail truck in our neighborhood while I took my dog outside. 

Because of this debacle, I started reading USPS employee testimonies online. I discovered my father's story was not the only one. This behavior by supervisors not only occurs in my local California city, but in other states as well. Below are links where you can read countless stories about USPS employees who received similar treatment by upper management.

1. 501 responses (click Older Comments near bottom of page to scroll through them) in this article "The U.S. Postal Service is a Toxic Work Environment." The writer also witnessed 3 suicides in 2 years at his local USPS district: http://postalemployeenetwork.com/news/2010/04/the-u-s-postal-service-is-a-toxic-work-environment/
2. Another article with comments from employees from various states: http://www.overcomebullying.org/the-postal-service-has-shown-that-they-are-above-the-law.html
3. A forum post by someone who loved their job, but became very concerned about harassment by their supervisor: https://forum.federalsoup.com/default.aspx?g=posts&t=46771#post517660

For this to occur to so many employees in different locations, I can only come to the conclusion that this behavior by supervisors is universally allowed by higher-ups, or in the worst case scenario possibly encouraged. Supervisors are not being held accountable, and all blame falls on the CCAs. Besides being morally wrong, USPS is wasting taxpayer money by hiring a very large number of CCAs, over half of which will end up quitting or get fired. Maybe you've noticed that the USPS is hiring over the radio or in other advertisements. How much money is going into these advertisements and into the hiring process to find workers who they don't even plan on retaining?

Can you blame CCAs for quitting when they are facing this level of harassment? It is unacceptable that a federal organization allows such a hostile work environment. The Homeland Security and Governmental Affairs Committee in the Senate has jurisdiction over the United States Postal Service. I hope that our senators can implement change to protect workers from harassment in the USPS workplace. If the law will punish USPS for their actions, they will have to change their ways.