Suppose, for example, that Duncan Thurly is willing and able to pay $3 for a Hot Momma Fudge Bananarama Ice Cream Sundae. This is his demand price. However, the going market price, the actual price that everyone pays for a Hot Momma Fudge Bananarama Ice Cream Sundae at the Hot Momma Fudge Bananarama Ice Cream Shoppe is $2. While Duncan is willing and able to pay $3, he pays only $2. He receives a $1 consumer surplus on this purchase.

A Visual Representation

Consumers' Surplus

The demand price of Yellow Tarantulas is measured on the vertical axis and the quantity demanded is measured on the horizontal axis. The negatively-sloped demand curve captures the law of demand relation between these two variables. Key to this discussion, the demand price represents the maximum price that buyers are willing and able to pay. However, they often end up paying less.

For example, if the quantity demanded is 20 Yellow Tarantulas, then the demand price is $40. However, if the quantity demanded is 80 Yellow Tarantulas, then the demand price is $10.

Now suppose that the going market price of Yellow Tarantulas is $30. If so, buyers are willing and able to purchase 40 Yellow Tarantulas. Click the [Going Price] button to highlight this situation. However, while the demand price for the 40th Yellow Tarantula is $30, the demand prices for the other 30 Yellow Tarantulas are greater than $30. For example, the buyer who purchased the 20th Yellow Tarantula is willing and able to pay $40.

Yet, because the market price is only $30, the 20th Yellow Tarantula is purchased for $10 less than the maximum demand price. The difference between the demand price and the price paid is consumer surplus. This particular buyer gains $10 worth of consumer surplus. In fact, every Yellow Tarantula sold up to the 40th generates consumer surplus for the buyer. The 40th Yellow Tarantula is the only one with a match between demand price and price paid and no consumer surplus.

The total consumer surplus associated with a $30 price can be revealed by clicking the [Consumers' Surplus] button in the exhibit. The yellow triangle beneath the demand curve, but above the $30 price, is the consumer surplus.

The size of this consumer surplus triangle--while probably evident, but worth stating and demonstrating explicitly--depends on the price of the good. A higher price results in a smaller consumers's surplus and a lower price generates a larger consumer surplus. A click of the [Higher] and [Lower] buttons will reveal these alternatives.

Producers' Surplus