The traditional economic system is the most traditional and ancient types of economies in the world. Vast portions of the world still function under a traditional economic system. These areas tend to be rural, second- or third-world, and closely tied to the land, usually through farming. In general, in this type of economic system, a surplus would be rare. In a command economic system, a large part of the economic system is controlled by a centralized power. For example, in the USSR most decisions were made by the central government. This type of economy was the core of the communist philosophy. In a free market economy, firms and households act in self-interest to determine how resources get allocated, what goods get produced and who buys the goods. This is opposite to how a command economy works, where the central government gets to keep the profits. A mixed economy is a combination of different types of economic systems. This economic system is a cross between a market economy and command economy. In the most common types of mixed economies, the market is more or less free of government ownership except for a few key areas like transportation or sensitive industries like defense and railroad.