it must be a logical deduction; the more entended a state, the more corrupted as it is..
Even ancient philosophers admits it IDK who said "governers are the ones in a society who have the privilages of liying"..
İf you think about Rome, AS, later Arsacids became very corrupted. In Rome local governors tried to be emperor, in AS and Arsacids local governors tried to be king themselves in their land.
Both empire were declined even arsacid kingdom died because of the rise of the power of local governors.(Strap of Parsa, a strap of the king managed to capture whole kingdom even killed the king!)
So the size of an empire also determines what size of corruption she has.