What it means
Each seller has a minimum price they will accept, which depends on the cost of producing one more unit. A farmer might be willing to sell the first bushel for $20 and the hundredth for $35 because the extra units cost more to produce.
If the market price is $50, every unit sold at that price earns the seller more than their minimum. The sum of those differences across all units sold is the producer surplus.
It is closely related to profit, but not identical. Producer surplus ignores fixed costs and looks only at the gap between price and the marginal (extra) cost of each unit, so it is usually larger than profit.
Economists use it alongside consumer surplus, the benefit buyers get from paying less than they were willing to pay. Together, the two measure the total gain from trade in a market and show how a change such as a tax, a subsidy or a price cap affects each side.
For business, producer surplus helps explain who gains from price changes. When prices rise because of higher demand, sellers with low costs gain the most, while a price cap can reduce the surplus and lead some producers to leave the market.
Real-world calculations need care because the marginal cost curve is rarely known exactly. Managers usually estimate it from cost data and use the result as a guide, not as an exact figure, and they should state clearly which costs were treated as variable.
In practice
Real-world examples.
Example
A coffee grower can cover costs at $2 a kilogram but sells at $3.50 because the market price has risen. Her producer surplus per kilogram is $1.50. On 20,000 kilograms, that is a surplus of $30,000. If the price drops to $2.50, the surplus falls to $10,000.
Example
A government introduces a price cap on bread below the current market price. Bakers receive less per loaf, and their producer surplus falls. Some small bakeries find it no longer worth producing and close. The shortage that follows leaves consumers worse off as well.
Example
A manufacturer of electric bicycles benefits when demand rises and prices climb from $900 to $1,000. Every bicycle sold at the higher price earns an extra $100 above its previous margin. The most efficient factory gains the most. The manufacturer uses the extra surplus to fund a larger plant.
Formula
Calculation
Producer surplus = total revenue - total variable (marginal) cost of production
For a straight-line supply curve, producer surplus = 1/2 x quantity sold x (market price - lowest price at which supply begins)
Suppose a market price of $50, a supply curve that begins at $20 and a quantity sold of 1,000 units.
Producer surplus = 0.5 x 1,000 x (50 - 20) = 0.5 x 1,000 x 30 = $15,000.
Check: revenue is 1,000 x 50 = $50,000. Total variable cost is the average of $20 and $50 times 1,000 units, which is 35 x 1,000 = $35,000. Surplus is 50,000 - 35,000 = $15,000.Case study
Seen in the real world.
Hillcrest Dairy is an illustrative, fictional milk producer that sells 600,000 litres a month at the market price of $1.00 per litre. Its marginal cost rises steadily from $0.40 for the first litre to $1.00 for the 600,000th litre, increasing by $0.10 for every extra 100,000 litres.
The owner used the straight-line formula to estimate her producer surplus. It came to 0.5 x 600,000 x (1.00 - 0.40) = $180,000 a month.
In this illustrative story a new rule capped the milk price at $0.80. At that price she would produce only the litres whose marginal cost is below $0.80, which is 400,000 litres, and her surplus fell to 0.5 x 400,000 x (0.80 - 0.40) = $80,000. The cap therefore removed $100,000 a month of surplus and led her to cut output by a third.
Watch out
Common mistakes.
- Treating producer surplus as the same as profit, when it ignores fixed costs.
- Forgetting that surplus depends on the market price, so it changes whenever the price moves.
- Assuming that a higher price always benefits every seller equally, when low-cost producers gain more because the gap between their costs and the price is wider.
Questions
People also ask.
What is the difference between producer surplus and consumer surplus?
Producer surplus is the gain to sellers from receiving more than their minimum price, while consumer surplus is the gain to buyers from paying less than their maximum price.
How does a tax affect producer surplus?
A tax usually lowers the price sellers receive after tax, which reduces their surplus and can reduce the quantity sold, so the burden of the tax is shared between buyers and sellers.
Can producer surplus be negative?
Not for a seller who chooses to sell, since they would not sell below their minimum price, but total profit can still be negative once fixed costs are counted.
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