Ferris, you ask what possible effect traffic levels could have on efficiency.
The effect is collossal- just compare the way aircraft are handled at some of our low traffic density class D airports compared to one of our GAAP airports or say the way traffic is handled at Darwin compared to Sydney or LAX.
I have been fortunate to fly as pilot in command in many countries around the world and I have found that the holding, diversions and delays nearly always come from the low traffic density airports.
This is often because they have not introduced modern and efficient procedures