Source: Chapter 11 Q&A, Intro to Microeconomics, University of Texas at Austin
Price discrimination is when a firm charges different prices to different customers (or groups) for the same product, based on willingness to pay rather than differences in cost. It works only when the firm has market power, can prevent resale, and can sort buyers by elasticity. There are three degrees: first (charge each buyer their maximum), second (quantity discounts), and third (group-based pricing such as student or senior discounts).
Difficulty: Intermediate | Prerequisites: Basic monopoly theory (Chapter 10), understanding of marginal revenue, marginal cost, and consumer/producer surplus.
This chapter builds on single-price monopoly (Chapter 10) and asks: what if a monopolist could charge more than one price? Price discrimination is one of the most testable topics in introductory microeconomics because it ties together demand curves, marginal revenue, consumer surplus, producer surplus, and deadweight loss. If you are comfortable with how a single-price monopolist picks quantity and price (MR = MC), you are ready for this material. If that still feels shaky, revisit Chapter 10 first.
Price discrimination
Charging different prices to different buyers for the same good or service, where the price difference is not explained by a difference in cost. In simple terms, it means the seller tries to capture more of each buyer's willingness to pay instead of settling for one flat price.
Reservation price (willingness to pay)
The maximum amount a buyer would pay for one unit of a good. Think of it as the buyer's personal ceiling: they will buy at any price at or below this number and walk away above it.
First-degree (perfect) price discrimination
The seller charges every buyer their exact reservation price. In simple terms, the firm extracts every last pound of consumer surplus, leaving buyers with none. Consumer surplus and deadweight loss both fall to zero; all surplus becomes producer surplus.
Second-degree price discrimination
The seller offers different pricing tiers based on the quantity or version purchased, letting buyers sort themselves. Think of it as bulk discounts or "buy two, get one free" deals: the firm cannot observe each buyer's type directly, so it designs the menu so that each type picks the option meant for them.
Third-degree price discrimination
The seller divides buyers into identifiable groups (students, seniors, military) and charges each group a different price based on differences in price elasticity of demand. In simple terms, groups with fewer alternatives or less price sensitivity pay more; groups that are more price-sensitive pay less.
Consumer surplus
The difference between what buyers are willing to pay and what they do pay, summed across all buyers. Graphically, it is the area below the demand curve and above the market price.
Producer surplus
The difference between the price received and the marginal cost, summed across all units sold. Graphically, it is the area above the supply (or MC) curve and below the price.
Deadweight loss
The total surplus that is lost because the quantity traded is below the socially efficient level. Under single-price monopoly, it is the triangle between the demand curve and the MC curve, to the right of the quantity produced.
Marginal revenue (MR)
The additional revenue from selling one more unit. For a price-setting firm, MR falls below the demand curve because lowering the price to sell an extra unit also lowers the price on all previous units.
Socially efficient quantity
The output level where the demand curve crosses the MC curve. At this quantity, every unit whose value to the buyer exceeds its cost gets produced, and total surplus is maximised.
The seller knows each buyer's reservation price and charges exactly that amount.
Every unit where the buyer's willingness to pay exceeds marginal cost gets sold.
The firm produces the socially efficient quantity (same as perfect competition).
All surplus goes to the producer. Consumer surplus = 0, deadweight loss = 0.
Example: a golf instructor who knows each client's maximum willingness to pay and sets the fee just below it. A car dealer who negotiates individually with every customer is a rougher version of the same idea.
The seller cannot observe each buyer's type but designs a menu of options that makes buyers self-select.
Pricing is based on quantity purchased, product version, or bundling, not on who the buyer is.
Examples: "buy two, get one free" at a pizza shop; bulk discounts at warehouse stores; economy vs. business class on flights.
The key mechanism is that buyers reveal their own price sensitivity by the option they choose.
The seller sorts buyers into identifiable groups and charges each group a different price.
Groups with more inelastic demand (fewer substitutes, higher need) pay a higher price.
Groups with more elastic demand (more substitutes, more price sensitivity) pay a lower price.
The firm sets MR = MC separately in each submarket.
Examples: student discounts at cinemas, senior discounts at theme parks, weekday vs. weekend bus fares, early-bird dinner discounts at restaurants.
A single-price monopolist produces where MR = MC, charges the price on the demand curve at that quantity, and creates deadweight loss (the triangle to the right of that quantity, between demand and MC).
A perfect price discriminator produces where the demand curve meets MC, charges each buyer their reservation price, and eliminates deadweight loss entirely. The old consumer surplus and deadweight loss areas all become producer surplus.
A firm must satisfy three conditions to price discriminate effectively:
Market power (downward-sloping demand curve). A price taker in a perfectly competitive market cannot price discriminate because it has no control over price. The firm must be able to set its own price, which requires some degree of monopoly power.
Ability to prevent resale (no arbitrage). If the low-price group can buy the good and resell it to the high-price group, the price difference collapses. Services (haircuts, tutoring, cinema tickets) are naturally hard to resell. Physical goods are harder to protect.
Ability to identify and separate groups with different elasticities of demand. The firm must be able to sort buyers into groups that differ in their price sensitivity and then charge each group accordingly. Student IDs, age verification, coupon redemption, and time-of-purchase are common sorting mechanisms.
Senior and student discounts at cinemas (Regal Cinemas, Disneyland). Seniors and students tend to have more elastic demand. Charging them less fills seats that would otherwise go empty, while full-price tickets capture surplus from less price-sensitive adults. This is third-degree price discrimination.
Early-bird dinner discounts. A restaurant offering 20% off between 4 and 6 pm is sorting customers by price sensitivity. Those willing to eat at odd hours get a lower price; those who want peak-hour convenience pay full price.
Weekend bus rides free, weekday fares charged. Commuters who need the bus for work have inelastic demand and pay more per trip on average. Casual weekend riders have very elastic demand (they could just not ride), so the free weekend fare brings them in without sacrificing weekday revenue.
Coupons and rebate offers. Manufacturers who offer coupons are sorting customers: only the more price-sensitive buyers bother to clip and redeem them. Those who do not redeem reveal lower price sensitivity and pay the full shelf price.
Last year's editions at half price (bookstores). Buyers willing to pay full price for the current edition do so. Price-sensitive buyers wait for the older version at a discount. The store captures surplus from both groups.
Airline pricing. Airlines charge business travellers (who book late, need flexibility) more than leisure travellers (who book early, accept restrictions). Price discrimination leads to more total passengers flying, not fewer.
"A clearance sale is price discrimination." Students often confuse markdowns on perishable or seasonal inventory (Easter candy at 50% off) with price discrimination. A clearance sale reduces price because the product's value has fallen, not because the seller is sorting buyers by willingness to pay. That is not price discrimination.
"Price discrimination always hurts consumers." Under perfect price discrimination, consumer surplus does fall to zero. But third-degree discrimination can lead to more total output and lower prices for the elastic group, which means some consumers are better off than under single-price monopoly.
"The firm must know each buyer's exact willingness to pay." Only first-degree discrimination requires that. Second- and third-degree discrimination work with rougher information: group membership (third degree) or self-selection through menu design (second degree).
"Price discrimination requires charging a higher price." It requires charging different prices. The firm charges more to the inelastic group and less to the elastic group. Charging everyone the highest possible price is not price discrimination; it is just monopoly pricing.
⚠️ Know the three conditions for effective price discrimination cold. Multiple-choice questions test whether a firm has a downward-sloping demand curve, can prevent resale, and can identify groups with different elasticities.
⚠️ Be able to identify which degree of price discrimination an example illustrates. The exam often gives a scenario and asks you to classify it.
⚠️ Understand what happens to consumer surplus, producer surplus, and deadweight loss when a single-price monopolist switches to perfect price discrimination. Producer surplus expands to cover the entire area between demand and MC; consumer surplus and deadweight loss both go to zero.
⚠️ Know that price discrimination generally increases total output (more customers served) compared to single-price monopoly. Airlines flying more passengers is the standard example.
⚠️ Be able to work through the marginal revenue table for a monopolist facing individual buyers with different reservation prices. The tutoring problem (Question 2) is the classic exam format for this.
True or false: A clearance sale on leftover seasonal goods is an example of price discrimination.
False. The price drop reflects a fall in the product's value, not sorting by willingness to pay.
Fill in the blank: For price discrimination to work, a firm must have a ______ demand curve, be able to prevent ______, and identify groups with different ______.
downward-sloping; resale; elasticities of demand.
True or false: Under perfect price discrimination, deadweight loss is zero.
True. The firm produces the socially efficient quantity.
Fill in the blank: Second-degree price discrimination relies on buyers ______ into the right pricing tier.
self-selecting (or sorting themselves).
True or false: When an airline price discriminates, fewer total passengers fly.
False. Price discrimination generally increases total output.
Q: Which of the following is NOT a good example of price discrimination? (a) UT charges students less for football tickets. (b) Target puts leftover Easter candy on 50% clearance. (c) Manufacturers offer lower prices to coupon shoppers. (d) Disneyland charges seniors $20 less.
A: (b). The Easter candy markdown reflects reduced value of a seasonal good, not sorting by willingness to pay.
Q: What three conditions must a firm meet to price discriminate effectively?
A: It must have a downward-sloping demand curve (market power), be able to prevent resale, and be able to identify at least two groups of customers with different elasticities of demand.
Q: Which is the best example of a firm that price discriminates? (a) Coldstone (b) Old Navy (c) Target (d) Regal Cinemas
A: (d) Regal Cinemas, which charges different ticket prices to seniors, students, children, and adults.
Q: A pizza shop offers "buy two, get one free." What degree of price discrimination is this?
A: Second-degree. The discount is tied to the quantity purchased, and buyers self-select.
Q: A golf instructor charges each client a fee just under their maximum willingness to pay. What type of price discrimination is this?
A: First-degree (perfect) price discrimination. The instructor knows each buyer's reservation price and charges accordingly.
Q: When an airline price discriminates, does this lead to (a) fewer customers flying, (b) more customers flying, (c) higher prices, or (d) lower prices?
A: (b) More customers flying. Price discrimination increases total output by serving price-sensitive passengers who would not fly at the single monopoly price.
Q: For price discrimination to be effective, the firm must: (a) charge everyone the highest price, (b) lower its price to attract more customers, (c) identify at least two groups with different elasticities of demand, or (d) charge those with elastic demand more?
A: (c). The firm must identify groups that differ in price sensitivity and charge accordingly.
Price discrimination connects directly to monopoly theory (Chapter 10). The single-price monopolist's MR = MC decision is the starting point; price discrimination asks what happens when the firm can do better than one price. It also ties into elasticity (Chapter 5): the entire logic of third-degree discrimination rests on groups having different price elasticities. Finally, the welfare analysis (consumer surplus, producer surplus, deadweight loss) revisits the tools from Chapters 4 and 6, applied to a market with a single seller.
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