I understood what they meant although it isn't the right way in doing it. See if they put this varying tax rates system, you no longer would need to think much about what to build in some settlements because you just adjust the tax to compensate for the stability of that settlement especially as your empire grows. build a lot of money producing buildings that produce squalor but you lower the taxation on that settlement to ease the population which defeats the purpose. When one is having a problem with a settlement that has increasing unhappiness, instead of exempting the province from taxation or doing anything else to curb the problem, you can just adjust the taxation rate to stabilize the settlements and not only will the problem be solved right away, you will still get money albeit lower. It takes time and makes management of your provinces' stability easier. Without this system, you need to think carefully on how to use agents, what to build to avoid instability, and think about the enemy's movement in the region.