instead of just adding to your income, it adds a percentage of ALL Commerce income for the Commandery. It also adds a +xxx% increase in Commerce income. Inns adds something a little different though than just increasing income (Commerce).
The second set of buildings requires the "Tea" resource, acquired from the Tea House minor settlements. This is the other obvious choice for building your economy. Make sure you can get a hold of this resource as soon as you can. This makes "Copper" honestly the most valuable resource in the game. It's important to note that the level four and level five buildings require the "Copper" resource, acquired from Copper Mine minor settlement.
#TOTAL WAR THREE KINGDOMS SETTLEMENT ADMINISTRATION UPGRADE#
The level five upgrade passes on a 15% reduction instead. The level four upgrade increases income by only 50 (Industry), it does a remarkable thing: it passes on that 10% corruption reduction to all adjacent Commanderies. This upgrade is essential, as it is the primary way to keep your economy stabilized. At level two, the next upgrade can either be the "government Workshops" building, granting 300 income (Industry), or the "Currency inspectors Office" building, while which only granting the same 200 income (Industry), now adds a 10% corruption reduction.
While this building Chain seems like a fairly obvious choice to add, since it increases income by 100/200/300/400/500 (Industry), there is another reason why this building is ultimately important. There are 5 buildings that in general, should be built in practically all of your Commandery Capitals: I'm sure there are probably better ways to do this, but at the very least, this should hopefully help people to just can't wrap their heads around the games economy. I've gone from barely able to afford 4 to 5 armies late game to well over 14 armies in fewer turns.
I've been trying out different ways of making an economy work for about 200 hours now, and I think I've found a combination of buildings and tactics that seem to work out. I can easily see why, as the addition of the corruption mechanic, as well as the fact that building up an economy is a bit less straight-forward than in previous total war games, where there is typically just one or two buildings that are obvious to build. One thing that I've noticed since the game had come out is that some people still have problems with creating and maintaining a good economy.