The Common Market or CM is a group of countries and Enterprises that decided to unite in trading their products between themselves. The more they are able to trade with each other the better. They try to avoid selling their products on the international market while becoming less dependent on products from the world market.
Trading on a Common Market is the trading between players who joined the same Common Market. Members of a common market can increase their score by trading goods on the common market instead of offering and purchasing their goods.
To trade on a Common Market, you can create long-term contracts with corporations and countries of other members of the same Common Market. Up to 25 players can join in a Common Market. You can be a member of one Common Market only. In the real world common markets exist to promote free trade by reducing artificial costs and barriers. In Simcountry a common market essentially provides trade contracts among members at market rate prices.
Many players join common markets but are not active in them. Unless contracts are manually offered and accepted, and periodically updated if necessary, membership can be useless.
Most veteran players regard common markets as counterproductive. According to that view, it's more profitable to sell products outside of a common market at prices higher than the market rate.
However, a common market can be a useful way to network with other players. Their messaging features can improve communication among many players. An active common market can serve as a forum for players to do favors for each other.
Advantages and Disadvantages
A common market contract is profitable if you're selling products in surplus, and saves money if you're buying products in shortage.
A common market contract is less profitable if you're selling products in shortage, and could cost more money if you're buying products in surplus. A big disadvantage is that a common market is not as automated as it seems. Production contracts above the common market minimum must be manually offered, and all contracts must be manually accepted.
A crucial issue are common market contracts for country consumption. It's cheapest for a country to purchase its supplies at 100 quality. There is no benefit for a country to consume higher quality products. But if a country buys its supplies from a common market, most of them will be at a quality above 100. That means the country would be wasting money by buying its supplies from a common market. It's almost certainly cheaper for the country to buy its supplies from the open market, with an automated setting of 100 quality.
In other words, a common market might financially benefit country corps or CEO corps. But it probably would financially hurt a country.
A common market is just a tool, kind of like a CEO is a tool. Whether or not one profits from a common market depends on how one uses it. So the real issue is whether one can figure out how to get more advantages than disadvantages. That depends on the strategy one uses and the corps one has, and which contracts one offers and accepts.
First of all, Common Markets can either be very useful or be real disasters...many former and current leaders have had 'bad experiences' with these in the past and often berade or bemoan the failure of 'all', but that simply isn't true...though, practically, yes, many common market are poorly organized, with void leadership and poor strategies and training, which does cause them to often be failures. However, if you choose one of the successful ones available, like GRCM on Golden Rainbow, you'll find that common markets can be a great success, boosting profits and creating very successful Empires and enterprises.
Check the common market blog at: http://blogs.simcountry.com/CorporatePartner
You can find an archive of many posts and comments, as well as guides and discussions, including actual transcripts of live chats with leaders who have discussed, trained and joined a successful common market.
The basic concept, however, is that contracts can stabilize and grow corporations very well, as well as provide a cheap way to supply corporations, boost produced quality, and gain very large profits. Te key is managing quality, mostly, which means that you want to contract all corporation supplies that cost less than about 1,000 SC$ per unit (world market price at 100 quality) to get maximum quality increases for minimal cost, generally speaking. This results in the average supply quality increasing to about 190 or higher which then gives your corporation products the maximum produced quality possible, so they sell for a higher price and faster. Selling on contracts also boosts market value and keeps product moving which also boosts the corporation productivity. While some products are sold to the world market naturally, many others can return as contracts for supplies to other corporations..and, in this way a common market--a good one--can provide many needed supplies with good availability for all members. The end result is usually a mix of contracts both buying and selling that generate very good profits for all members.