Value added - the gross value of the product minus the costs of raw materials and energy. Free market economy - an economic system in which means of production are largely privately owned and there is little or no government control over the markets. Supply and demand - in economies, the relationship between the amount of commodity that producers are able and willing to sell (supply) and quantity that consumers can afford and wish to buy (demand). Moral economy - visions of the world in which the needs of the community (providing food for the family, bread, grains, etc. ) dominated over the need for competition and profit. Trade diaspora - networks of interconnected commercial communities in major cities throughout africa, europe, and asia. Silk route - an ancient trade route between china and the mediterranean sea extending some. 6,440 km (4,000 mi) and linking china with the roman empire. Marco polo followed the route on his journey to cathay.