Federal employees will always tell you that they could make more money in the private sector.
That they SAY it means nothing. Where is the evidence that they have actually DONE IT? Federal retirement benefits are completely guaranteed once vested, so a civil service can easily leave AND, should it not pan out, probably have a re-hiring preference!
An interesting find on the subject is here, "Stay or Leave: Pros and Cons of Federal vs. Private Sector Employment". While pre-COVID (2017) the list of FED worker benefits vs. Private is impressive! (FYI: To the best of my knowledge, NO Federal Worker lost any pay, seniority or vacation while furloughed during COVID!)
FEDERAL Benefits:
Job Security, Retirement Benefits, Thrift Savings Plan, Federal Employee Health Benefits Program & Leave Programs.
Private Sector:
Pay (potentially higher than GS Schedule), Different Jobs/Duties (Not the 9-5 drudgery) and Benefits (Negotiable, Executive level perks, but uncertain) {Not in article but real: Stock Warrants & Options & ESOP Plans].
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So, yeah, I can see a large migration into Private Sector ... /sarcasm!