Mediocre and lazy/unproductive accounts for 90%+, I'd wager.
Kinda depends on the agency and the type of employee. Customer service types? Probably so. Among professionals, it wouldn't be that high, but it would be higher than in the private sector and much higher than in small businesses. The easier for the employee to hide in an institution and stay under the radar, the more common mediocrity and laziness are.