A price floor is a government- or group-imposed price control or limit on how low a price can be charged for a product, good, commodity, or service. It is one type of price support; other types include supply regulation and guarantee government purchase price. A price floor must be higher than the equilibrium price in order to be effective. The equilibrium price, commonly called the "market price", is the price where economic forces such as supply and demand are balanced and in the absence of external influences the (equilibrium) values of economic variables will not change, often described as the point at which quantity demanded and quantity supplied are equal. Governments use price floors to keep certain prices from going too low.