贸易区是由一连串被同一角色持有贸易站的省份组成,并为 直辖领收入和贸易站收入提供加成。 Trade zones scale super-linearly，因此最好有一个6省的贸易区，而不是两个3省的贸易区。
可以通过点击贸易区来看见该省属于哪一贵人家族的贸易区。
地图模式 (G)然后在按住Ctrl键的同时,点击共和国。
Contiguity（连续性）
For trade zone purposes, control of a sea province is determined by which family owns the most trade posts pointing into that sea province. If there is a tie, the sea zone is considered neutral: no family owns it, and no trade posts can be connected through it. If the sea zone is controlled by a family, all trade posts in adjoining land provinces are connected, regardless of port locations.
Trade value
The value of the trade zone is based on the income and holdings in the provinces with trade posts. Trade zone value also receives a large bonus from being connected to the republic's capital. Some buildings increase trade value as well.
收入加成
贸易区中的城市和贸易站可根据其贸易价值（TV）获得一定比例的收入加成，注意这个加成在城市上减半。
贸易区加成 = (TV * 100) / (TV + 200)
Disease spread
With 
Reaper's Due DLC, trade zones can help spread epidemics. Wealthy rulers should consider fortifying their trade zone provinces with upgraded hospitals.
Technology spread
Technology spreads unidirectionally from trade posts to the merchant republic capital.