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