Several factors contribute to the number of drones found at a base before police, facilities, psych, and secret projects are taken into account:

(1) Difficulty Level: at the lowest difficulty level, every citizen after the first six is a drone. For each increase in difficulty level, an additional drone is added, so at the highest level every citizen after the first one is a drone.

(2) Bureaucracy: depending on your EFFICIENCY and your difficulty level, you will receive additional drones when your number of bases exceeds a certain number. See Bureaucracy.

(3) Disloyal Citizenry: for approximately 50 turns after you capture an enemy base, you will receive extra drones while you assimilate the enemy citizens. The basic rate is 5 drones minus one for each 10 turns elapsed, but the number may never exceed:

(4) Faction Power: some factions receive additional drones or talents. For instance, the University receives an extra drone for every 4 citizens (rounded down), while the Peacekeepers receive an extra Talent for every 4 citizens, rounded up.