A few slightly more detailed comments:

You might want to mention expenditures like Family member wages (200 each I think, 300 for the Faction Leader), devastation, diplomatic tributes in your opening list. You might also want to mention one time incomes/expenditures, like Senate fines or selling map information.

Quote Originally Posted by Quietus
I have two test provinces with the same population and the same taxes, but the equation for this relationship is nary obvious.
You have two settlements with the same population, no Governors, same tax rate, same difficulty level, but have different tax incomes? I've never seen this in my games. Would you mind making the game available to me? I thought I had tax income pretty much solved. Ho hum.

Trade

In my games the increase due to paved roads is 100%. It's 50% for Highways. For increases in neighbouring settlements, it usually depends on the relative quality of their roads, from my limited experience.

Sea Exports/Imports - It's been my general observation, as yet unconfirmed, that your trading routes depend on a number of factors. Geography is one: you only seem to sea trade within a certain locality. Selection of routes is based on profitability of the route. The game automatically chooses the best route for trading. It takes into account trade agreements, and is strongly dependent on both the goods that you can trade to a settlement (i.e. if a target settlement has that resource as well, it will not be traded), and the populations of the two settlements.

Basically, the more populated the market is, the more money everyone gets (imports and exports). A very large city, which is centrally located around a number of large cities with lots of trade goods, will not only make a great deal from exporting, but also a fair amount from importing. This is why, along with tax income, you want your cities as large as you can make them.

Quote Originally Posted by Quietus
How he managed to calculate the distances by tiles, I do not know.
In the first instance, the fool counted squares from known landmarks (Wonders, for the most part). He then learned of the show_cursorstat RomeShell command. Unlike other RomeShell commands, you can use this as many times as you like. It's then just a question simple of trigonometry.

Trade Fluctuations - I suspect this is to do with population changes.