Any time there's an unfunded liability, particularly for things like employee future benefits, the way the discount rate is determined is by reference to the government's borrowing rate.
Now, different governments may end up with a different number. Some use what the borrowing rate is on that day, meaning how much it would cost the government to borrow on that year-end date. I think that the federal government uses more a blend of different borrowing rates, so there's a slight difference there, but in both cases it would be with reference to what the government's borrowing rate is.