# Deadweight Loss: Definition and How to Calculate It

By Matthew Zeitlin · September 27, 2023 · 8 minute read

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Deadweight loss is the term used to describe societal or economic losses caused out of inefficiencies. It’s an economic term, and refers specifically to losses created as a result of a lack of equilibrium in supply and demand models — or, in other words, when resources are not being used as efficiently as possible.

This can have larger impacts on the overall economy, which can trickle down and have an effect on the markets and on investors, too. As such, investors would do well to understand the concept, and how it may impact their portfolios.

As noted, deadweight loss refers to inefficiencies created by a misallocation or inefficient allocation of resources, and is an important economic concept. Deadweight loss is often due to government interventions such as price floors or ceilings, or inefficiencies within a tax system.

To understand more fully, it can be helpful to think about how government interventions can impact the equilibrium between supply and demand.

### First: How to Calculate Surplus

In order to know how to calculate deadweight loss, we must first be able to calculate surplus.

Typically, a business will only sell something if they can do so at a price that’s greater than what they paid for it themselves, and a consumer will only buy something if it’s at or less than the price they want to pay for it — the same principle as generating a stock profit.

Scenario A — The Equilibrium: Let’s imagine a store selling comic books for \$10 each. The store buys the comic books from the wholesaler for \$5 and sells them for \$10, pocketing \$5 of “producer surplus.” Before the store opened, comic book readers would go over to the other town to buy comic books for \$15, the price they were willing to pay, but now can buy them for \$10. This \$5 difference between the price they’re willing to pay is the “consumer surplus”.

In this case, let’s say the store is able to sell 1,000 comic books, that means the combined producer and consumer surplus is \$10,000.

Breakdown:

•  P1 = Producer’s Cost of a Comic Book = \$5

•  P2 = Producer’s Price to Sell a Comic Book = \$10

•  P3 = Price A Consumer Pays = \$10

•  P4 = Price A Consumer Is Willing to Pay = \$15

•  Units Sold = 1,000

•  Producer Surplus = (P2 – P1) * Units Sold = (\$10 – \$5) * 1,000 = \$5,000

•  Consumer Surplus = (P4 – P3) * Units Sold = (\$15 – \$10) * 1,000 = \$5,000

•  Total Surplus1 = Producer Surplus + Consumer Surplus = \$5,000 + \$5,000 = \$10,000

Deadweight loss can be found on a supply and demand graph, or supply and demand curve. That graph generally shows the relationship between supply and demand with two lines that intersect at an equilibrium point, with a downward-sloping demand line and an upward-sloping supply line.

On such a graph, deadweight loss can be found to the left of the equilibrium point, comprising both the consumer surplus and consumer surplus.

## Common Causes of Deadweight Loss

There can be several causes of deadweight loss, but some of the most common are government-mandated changes to markets. Examples include price floors, such as a minimum wage, which can create some inefficiencies in the labor market (there may be workers who would be willing to work for less than minimum wage). Price ceilings, also can create deadweight loss — an example could be rent control. Finally, taxes can create deadweight loss, too.

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## How to Calculate Deadweight Loss

To properly calculate deadweight loss, you need to be able to represent the supply and demand of the goods being sold graphically in order to determine prices. According to the laws of supply and demand, the higher a price goes, the fewer of that item will get sold; and vice versa.

Scenario B — Imposed Tax: Let’s go back to our comic book example and imagine that the town’s government imposes a \$2 tax on comic books.

What happens to the price of comic books and the surplus generated by the sales of comic books? If consumers had to buy comic books to live (and for some, it may feel that way) and there were no other way to buy them, then the comic book seller could simply bump up prices \$2 and sell 1,000 comic books for \$12 each, maintaining his \$5 of producer surplus on each comic book sold with \$2 going to the government and consumer surplus of \$3.

In this case the combined consumer and producer surplus is lower — \$5 × 1,000 + \$3 × 1,000 = \$8,000. So there’s a missing \$2,000 of what economics call “gains from trade.” But, the government is collecting \$2,000, so the money does not disappear from the economy.

The government can buy things, hire people, and literally send money to people, via economic stimulus, meaning the tax revenue does not disappear from the economy.

But, despite how fervently people want them, comic books are not a necessity in the same way food is and remember that comic book store in the neighboring town? If the demand for comic books can not literally be unchanged by its price, that means the comic book seller may think twice about passing on the tax fully on to his customers and that any price increase will result in some comic books going unsold.

If he were to increase the price to \$12, thus passing on the tax to his customers, he may not be able to sell enough comic books to maintain the revenue he needs to keep his store open, so he lowers the price to \$11, thus splitting the tax between himself and his buyers but still reducing the number of total comic books sold. In this case, let’s say he sells 600 comic books instead of 1,000.

The combined consumer and producer surplus is \$4,800 (\$4 × 600 + 600 × \$4) with \$1,200 of tax collected (600 × \$2) meaning there’s a total of \$6,000 of consumer surplus, producer surplus, and government revenue. In this case the deadweight loss is \$4,000.

Breakdown:

•  P1 = Producer’s Cost of a Comic Book = \$5

•  P2 = Producer’s Price to Sell a Comic Book = \$9

•  P3 = Price A Consumer Pays = \$11

•  P4 = Price A Consumer Is Willing to Pay = \$15

•  Units Sold = 600

•  Tax = \$2/Comic Book

•  Producer Surplus = (P2 – P1) * Units Sold = (\$9 – \$5) * 600 = \$2,400

•  Consumer Surplus = (P4 – P3) * Units Sold = (\$15 – \$11) * 600 = \$2,400

•  Gains From Trade (Tax) = \$2 * 600 = \$1,200

•  Total Surplus2 = Producer Surplus + Consumer Surplus + Gains From Trade = \$6,000

•  Deadweight Loss = Total Surplus1 – Total Surplus2 = \$10,000 – \$6,000 = \$4,000

The higher price, created through taxation, has impacted the equilibrium between supply and demand and created a deadweight loss — the surplus that evaporates due to fewer transactions happening between the comic book seller and the readers.

While this is a rather extreme example of what happens when taxes force up prices, it’s a good way of thinking about how deadweight losses are more than just items getting more expensive. Rather, the deadweight loss formula can illustrate the evaporation of mutually beneficial economic transactions due to different types of taxes.

Deadweight loss of taxation refers specifically to deadweight loss that occurs due to taxes, but a similar impact can occur when a government puts price floors or ceilings on items.

Deadweight loss can affect investors in a number of ways, and it’s important to consider it when looking at different types of investments. One of the most debated issues in economics is the effects that the tax system has on income, investment, and economic growth in the short and long run.

Some argue that income taxes, payroll taxes (the flat taxes on wages that fund Social Security and Medicare) and capital gains taxes work like the comic book tax described above, preventing otherwise beneficial transactions from happening and reducing the economic gains available to all sides. There’s evidence on all sides of this debate, and the effects of tax rates on overall economic growth are, at best, unclear.

As an investor, deadweight loss might matter when it comes to companies or sectors impacted by specific taxes, such as sales taxes or excise taxes on alcohol or cigarettes. Deadweight loss shows how taxes on specific items can not only reduce profitability by increasing a company’s tax bill, but also affect revenue by reducing overall sales or driving down prices that businesses can charge or receive from buyers. As an investor, this knowledge and insight can be useful when allocating capital between companies, sectors, or types of assets.

## The Takeaway

Deadweight loss is the result of economic inefficiencies, and it can affect an investor’s portfolio if it results in slower sales and revenues for businesses. It’s a large economic concept, and may not have a day-to-day direct impact on the stock market. But it’s still good for investors to know the basics of deadweight loss and how it applies to them.

There are myriad economic concepts investors should pay attention to, and deadweight loss is merely one of them. Studying deadweight loss and related concepts can help investors plan for the future and work toward their financial goals.

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## FAQ

### Why does a monopoly cause a deadweight loss?

A monopoly can cause deadweight loss because competitive markets create competition and fairer prices. A monopoly distorts prices, leading to inefficiencies.

### Can deadweight loss be a negative value?

No, deadweight loss cannot be a negative value, but it can be zero. Zero deadweight loss would mean that demand is perfectly elastic or supply is perfectly inelastic.

### Is deadweight loss market failure?

Deadweight loss is not a market failure, but rather, the societal costs of inefficiencies within a market. Market failures can, however, create deadweight loss.

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