Trade taxes

Trade taxes are a form of province income generated in all trading posts and settlements.

The computation of trade taxes is fairly simple. Each province generates a "base" level of trade tax (called here the BTT), based on the size of the trading post or settlement. This number is then multiplied by the owning country's trade efficiency percentage, plus one. That is,

 trade_tax = base_trade_tax*(trading_efficiency + .01)

The base trade tax for trading posts and colonies is their level, in ducats. That is, a level 5 trading post has 5 ducats for its base trade tax. A level 8 colony (800-899 population) has 8 ducats of base trade tax. For cities, the base trade tax is a logarithmic function of population, according to this table:

 Population    BTT
 1000-5000     10
 5001-10000    11
10001-20000    12
20001-40000    13
40001-80000    14
80001-200000   15
   200001+     16

As is the case for other forms of province income, when an enemy army has covered or controlled a province, it generates no trade taxes.