Corruption | Economy Eador: MotBW Guide

Large kingdoms struggle with corruption - if the kingdom grows too extensive, some portion of revenues will start going missing. The scope of the problem is determined by the difficulty level:

Corruption levels can be minimized with buildings from Central Quarter category. They are, however, so expensive that it makes sense to invest in them only later in the game. Before you get to that point, the best way to counter corruption is to... restrain your expansive impulses and avoid provinces populated by goblins and dwarves. These are the two races that increase crime the most (see: Races).