Producer Surplus

What Is a Producer Surplus?

Producer surplus is the difference between how much a person would be willing to accept for given quantity of a good versus how much they can receive by selling the good at the market price. The difference or surplus amount is the benefit the producer receives for selling the good in the market. A producer surplus is generated by market prices in excess of the lowest price producers would otherwise be willing to accept for their goods. This may relate to Walras' law.

Understanding Producer Surplus

A producer surplus is shown graphically below as the area above the producer's supply curve that it receives at the price point (P(i)), forming a triangular area on the graph. The producer’s sales revenue from selling Q(i) units of the good is represented as the area of the rectangle formed by the axes and the red lines, and is equal to the product of Q(i) times the price of each unit, P(i).

Because the supply curve represents the marginal cost of producing each unit of the good, the producer’s total cost of producing Q(i) units of the good is the sum of the marginal cost of each unit from 0 to Q(i) and is represented by the area of triangle under the supply curve from 0 to Q(i). Subtracting the producer’s total cost (the triangle under the supply curve) from his total revenue (the rectangle) shows the producer’s total benefit (or producer surplus) as the area of the triangle between P(i) and the supply curve.

Total revenue - total cost = producer surplus.

The size of the producer surplus and its triangular depiction on the graph increases as the market price for the good increases, and decreases as the market price for the good decreases.

Image by Julie Bang © Investopedia 2019

Producers would not sell products if they could not get at least the marginal cost to produce those products. The supply curve as depicted in the graph above represents the marginal cost curve for the producer.

From an economics standpoint, marginal cost includes opportunity cost. In essence, an opportunity cost is a cost of not doing something different, such as producing a separate item. The producer surplus is the difference between the price received for a product and the marginal cost to produce it.

Because marginal cost is low for the first units of the good produced, the producer gains the most from producing these units to sell at the market price. Each additional unit costs more to produce because more and more resources must be withdrawn from alternative uses, so the marginal cost increases and the net producer surplus for each additional unit is lower and lower.

Consumer Surplus and Producer Surplus

A producer surplus combined with a consumer surplus equals overall economic surplus or the benefit provided by producers and consumers interacting in a free market as opposed to one with price controls or quotas. If a producer could price discriminate correctly, or charge every consumer the maximum price the consumer is willing to pay, then the producer could capture the entire economic surplus. In other words, producer surplus would equal overall economic surplus.

However, the existence of producer surplus does not mean there is an absence of a consumer surplus. The idea behind a free market that sets a price for a good is that both consumers and producers can benefit, with consumer surplus and producer surplus generating greater overall economic welfare. Market prices can change materially due to consumers, producers, a combination of the two or other outside forces. As a result, profits and producer surplus may change materially due to market prices.