Center of trade
A center of trade (universally abbreviated "CoT") is a building that represents a regional market. As the name suggests, centers of trade are the locuses of the trading subgame within EU2. Generated trade, which is created in all trading posts and settlements, always goes to some CoT. Countries may send merchants to centers of trade in order to trade there, thereby taking a fraction of the value of the trade as trading income. For their owner, settlements containing centers of trade are among the most valuable in the game due to the trade tariffs collected there.
Location and Display of CoTs
On the map, and on the province screen, CoTs are displayed in their host city. You can click on the building graphic in both places to go to the trading screen mode, including display of the center of trade screen.
The initial location of CoTs is fixed by the scenario. After the game starts, CoTs will disappear if they are not traded in actively. New CoTs will appear when there are relatively few of them. This is done semi-randomly; CoTs won't spring up near to others, and the game favors high-tax provinces for new CoTs.
The main purpose of CoTs in the game is as a place of trade, where countries can earn income from trade. To earn trade income in a CoT, a country must have one or more merchants present.
Each CoT has 20 merchant slots. Each slot may be filled by a merchant from a country; there may be fewer than 20 merchants in a CoT, but there cannot be more. To attempt to place a merchant into a CoT, you simply click the "Place Merchant" button there. Players call this process (clicking "Place Merchant" to attempt to place a merchant) "sending" merchants. Sending to a CoT, anywhere in the world, takes exactly one month. Merchants which are "in transit" are shown on the right of the CoT display.
Once sent, a merchant may or may not be able to establish himself in the CoT. This is a semi random event; even with empty slots, there is no guarantee. The chances of a successful send increase with a country's stability, its trade efficiency, and the administrative skill of its monarch. If all 20 slots are full on the day the merchant arrives, he cannot establish himself. However, he may be able to "compete out" a merchant from some other country. The opposing merchant is chosen randomly from among those in the 20 slots, so that a country with 5 merchants present is five times more likely to be chosen than a country with just one. (Exception: when a country is at war with, or has embargoed a second country, the first country's merchants will automatically target the merchants of the second.) Again, a random roll determines what happens, with the same factors applying, although this time from both countries. Two outcomes are possible: either the merchant is competed out and vanishes, thus freeing a slot in the CoT, or there is no effect. You will get a message when one of your merchants is competed out of a CoT; this is often a good time to send a new one.
Other Effects of CoTs
In addition to being able to trade there, CoTs have a number of other effects on the game.