The term surplus is used in economics for several related quantities. The consumer surplus (sometimes named consumer's surplus or consumers' surplus) is the amount that consumers benefit by being able to purchase a product for a price that is less than the most that they would be willing to pay. The producer surplus is the amount that producers benefit by selling at a market price mechanism that is higher than the least that they would be willing to sell for. Note that producer surplus generally flows through to the owners of the factors of production: in perfect competition, no producer surplus accrues to the individual firm. This is the same as saying that economic profit is driven to zero. Real-world businesses generally own or control some of their inputs, meaning that they receive the producer's surplus due to them: this is known as normal profit, and is a component of the firm's opportunity costs. If the markets for factors are perfectly competitive as well, producer surplus ultimately ends up as economic rent to the owners of scarce inputs such as land.
On a standard supply and demand (S&D) diagram, consumer surplus (CS) is the triangular area above the price level and below the demand curve, since intramarginal consumers are paying less for the item than the maximum that they would pay. In some schools of heterodox economics, the economic surplus denotes the total income which the ruling class derives from its ownership of scarce factors of production, which is either reinvested or spent on consumption. In Marxian economics, the term surplus may also refer to surplus value, surplus product and surplus labour.
Consumer surplus is the difference between the maximum price a consumer is willing to pay and the actual price they do pay. If a consumer would be willing to pay more than the current asking price, then they are getting more benefit from the purchased product than they spent to buy it. An...