A Civilization advance.
One of the oldest and most widespread social institutions is the exchange of goods, or trade. The most basic level of trade is barter--two people exchanging items with each other. The introduction of regulated currency that could be exchanged for items resulted in easier, more convenient trade. Merchants soon roamed the world, connecting different lands with webs of economic interdependence.
Prerequisites: Currency and Code of Laws.
Allows for: Banking and Medicine.

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