The introduction of mercantile practices in a nation adds a protective layer of taxes and bureaucratic procedures for goods imports and foreign traders which aims at promoting national trade, instead of depending on foreign merchants. The result is a very satisfied national merchant class, and they return the favor by providing additional financing for local governments when they wish to finish quickly some projects. Another beneficial effect is observed in the nation's financial institutions, such as banks and stock exchanges, in which young economists dig into the scientific basis of trading and produce some amazing research results. If not additional wealth...
- Purchasing items in Cities requires 25% less Gold.
- +1 Science from every Mint, Market, Bank, and Stock Exchange.
This is the most useful Policy of the entire Tree, hands down! It both boosts Science output for every economic building, and reduces Gold cost for all purchases with Gold in all cities! You are now able to use even more effectively all the Gold you earn through the other Policies in the tree - start purchasing important Buildings, instead of wasting turns to Produce them! This is especially useful in new cities, where Production capabilities are initially low.
Being a level 2 Policy, you can easily rush it by first adopting Mercenary Army. If you've managed to progress scientifically fast enough, and Commerce is your second tree, you should do exactly that. This way you will be able to use the Landsknechts, while at the same time gaining a significant boost to your mid-game Science output. Don't hesitate to start buying Universities right away - the tech progress boost is well worth the Gold cost, which is - surprise, surprise! - not that great anymore!
And of course, to make the most of this Policy, make sure you have as many buildings from the Commercial chain as possible (refer to the description above).
Mercantilism is a form of economic nationalism that encourages a nation to engage in policies of "protectionism" to promote its own exports and to limit imports from other nations. As a nation's "balance of trade" increases, the nation gains in wealth and prosperity, and if it dips below zero (the nation imports more stuff than it exports), the nation and its people grow poorer and more vulnerable to external threats. The theory was popular in Western Europe from the 16th to the 18th centuries. Today most western nations seek to open their borders to trade, albeit often with some level of taxation or quotas to protect their most important national industries.