Also, I find it ridiculous that retirement medical benefits can just be cut anytime, as they are part of the compensation agreement. It's just a fluke of the law that it was never enshrined like defined benefit pensions were.
I don't see where the USPS is required to use T-bill rates to value liabilities in the tex of the PAEA law:
https://www.govtrack.us/congress/bills/109/hr6407/text
>who shall hold membership in the American Academy of Actuaries and shall be qualified in the evaluation of pension obligations, to conduct a review in accordance with generally accepted actuarial practices and principles and to provide a report to the Commission containing the results of the review.
As to investing look at page 35-36. It’s not literally just T-bills, but treasury holdings with very low interest rates compared to the kinds of investments private companies are allowed to make.
https://about.usps.com/who-we-are/financials/10k-reports/fy2...
No they FedEx and UPS were required to prefund pensions in the 1970s, but they were given 40 years in which to do it.
USPS was given 10 years. In addition USPS was required to prefund retirement medical benefits, and unlike a private company who can cut retirement medical benefits at any time, USPS requires an act of congress to cut retirement medical benefits.
Furthermore, when calculating how much they need to set aside for retirement medical benefits, USPS can only use a much lower interest rate than private companies are allowed to use because they are forced to invest only in T-bills.