I was curious about this question so I did a google search. Curiously NASA came up several times as the most efficiently (or one of the most efficiently) run large department in the federal govt. I was surprised as it seems that historically they've had programs with massive cost overruns and delays similar to the Pentagon. What do people say here and why?
I've worked for the Federal government. Efficiency is never a metric. Metrics like fairness and inclusiveness (regarding how the citizenry is treated) makes efficiency irrelevant. Doesn't happen anywhere.