查看“贸易区”的源代码

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[[File:Map trade zones.png|500px|thumb|right|The trade zone map in 1066 (with Silk Road from [[Horse Lords]]/ [[Jade Dragon]] DLC in yellow)]]

[[File:Trade zone.png]] A '''trade zone''' is a contiguous set of provinces whose [[trade post]]s are owned by the same character. Trade zones give a bonus to [[demesne income|city income]] and trade post income. Trade zones scale super-linearly, such that it's better to have a single 6-province trade zone than two 3-province trade zones.

[[Patrician]] family trade zones can be viewed by clicking on the trade zone [[Keyboard_shortcuts#Map_modes|map mode]] ({{key press|G}}) and then clicking on a republic while holding down the Ctrl key.

==Contiguity==
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 [https://www.reddit.com/r/CrusaderKings/comments/4o30ew/does_anyone_understand_the_connected_to_capital/d49cswi/ connected to the republic's capital]. Some buildings increase trade value as well.

==Income bonus==

[[File:Trade value graph.png|300px|thumb|right|The trade zone bonus approaches +100% as the Trade Value approaches infinity.]]

Cities and trade posts within a trade zone receive a percentage bonus to their income depending on the trade value (TV) of the trade zone. Note that this bonus is halved for cities.

'''Trade Zone Bonus = (TV * 100) / (TV + 200)'''

==Disease spread==
With {{icon|trd}} ''Reaper's Due'' DLC, trade zones can help spread [[epidemic]]s. 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.

[[Category:商业共和国]]