Monopoly Graph Classroom Activities for AP Microeconomics

A monopoly graph activity earns its period only if students leave knowing why the profit-maximizing price is never the highest price a monopolist could charge. The six activities below use the graph's own logic, marginal revenue below demand, MR equals MC, the profit rectangle, to get there.

See it move

Make it move

A monopoly's price, quantity, profit and deadweight loss. Tap it to drag the curves, open the full version, or put it on your own site free, or turn it into a five-minute class activity.

A worksheet can ask a student to shade a deadweight loss triangle correctly. It cannot make them feel why a single seller facing the whole market demand curve behaves so differently from a price taker, which is the only reason this graph is on the exam at all. Open the live monopoly graph before the first activity so students see the curves move as the story unfolds.

1. The one-seller auction, 20 minutes

Pick one student to be the monopolist. Give every other student a card with a private willingness to pay for one unit of a fictional good, a range from very low to very high, shuffled and unlabeled. The monopolist announces a single price. Every student whose card clears that price buys one unit. Record price times quantity sold as revenue, then run it again at a different price.

Let the monopolist try three or four prices before revealing the true demand schedule and the marginal revenue that goes with it. Almost every class picks a high price first and watches quantity collapse, then a low price and watches revenue collapse the other way. The winning price sits in the middle, at the quantity where marginal revenue crosses marginal cost, not at the top of the demand curve.

The debrief question: why didn't the highest price win? Because raising price to squeeze more from the buyers who stay costs the monopolist every buyer who leaves, and that trade-off is exactly what marginal revenue measures. The misconception it exposes: the belief that a monopolist charges whatever it wants. It charges the price that maximizes profit, and that price is read up from the MR equals MC quantity to the demand curve, not chosen from the top of the graph.

2. The marginal revenue table race, 15 minutes

Hand out a demand schedule, six or seven price and quantity pairs, and nothing else. In pairs, students compute total revenue at each quantity, then marginal revenue as the change in total revenue per additional unit. First pair to finish a correct column wins, but the race is a pretext for what happens next.

Put the finished table on the board next to the original price column. Students see marginal revenue fall faster than price at every quantity past the first unit, and by mid-table it is negative while price is still positive. That gap is the entire reason the monopolist's marginal revenue curve sits below its demand curve on the graph, and it exists only because a single seller who wants to sell one more unit has to cut price on every unit it already sells, not just the new one.

The debrief question: why does marginal revenue fall faster than price? The misconception it exposes: that marginal revenue equals price, the rule that holds under perfect competition and nowhere else. Ask a few students to mark where MR turns negative and connect it to the elastic and inelastic ranges of demand they already know from the elasticity unit.

3. Predict then reveal, 8 minutes

Project the monopoly graph with a demand curve, a marginal cost curve, and no marginal revenue curve drawn in yet. Ask students to sketch, on paper, where they think MR belongs relative to demand, and to mark where they think price and quantity land. Then reveal the true MR curve and the MR equals MC quantity, and have them check their own sketch against it.

Most students draw MR on top of demand, or draw it as a curve that ends where demand ends. Neither is right, and the gap between a private guess and the reveal is what makes the correction stick, far more than watching a teacher draw it once. Follow the quantity straight up to demand to find price, not up to marginal cost, since that second error is nearly as common as the first.

The debrief question: at the MR equals MC quantity, why do you read price off demand and not off marginal cost? The misconception it exposes: treating MR equals MC as the price rule instead of the quantity rule, when price is a separate step that uses the demand curve.

4. Regulate the monopoly, 25 minutes

Split the class into two sides arguing before a mock regulatory board over a monopoly utility. One side must propose the socially optimal price, where marginal cost crosses demand, and defend it as efficient. The other must propose the fair-return price, where average total cost crosses demand, and defend it as the price that keeps the firm in business. Both sides draw their proposed price and quantity on the graph before they argue.

The tension is real: the socially optimal price often sits below average total cost, which means the firm loses money at the price that eliminates deadweight loss. Push the fair-return side to say what happens to the firm at the efficient price, and push the socially optimal side to say what happens to consumers at the fair-return price. Neither answer is comfortable, which is the point.

The debrief question: can a regulator set the efficient price and keep the firm solvent at the same time? The misconception it exposes: that regulation just means forcing a lower price, when the two regulated prices sit at different points on the same graph and trade off efficiency against the firm's survival.

5. The natural monopoly case, 15 minutes

Give students a firm whose average total cost keeps falling as it produces more, a natural monopoly where one large producer serves the market more cheaply than several small ones could. Have them locate where marginal cost sits relative to average total cost on the graph, then ask what happens to the fair-return price if a second firm tries to enter and split the market.

Splitting demand between two firms means each produces less, and less output pushes each firm further up a still-falling average cost curve, so both charge more than the single firm would have. That is why the graph, not a policy preference, is the argument for allowing one regulated seller instead of forcing competition.

The debrief question: would splitting this market between two firms lower prices or raise them? The misconception it exposes: the assumption that more competitors always means lower prices, which fails whenever average total cost is still falling at the relevant quantity.

6. Price discrimination, then the sandbox closer, 15 minutes

Return to the auction from activity one, but this time let the monopolist see the cards of six or eight volunteers and quote each one a personal price, rather than replaying the whole class. Revenue from those volunteers jumps because the monopolist captures willingness to pay that a single uniform price left on the table. On the graph, this is the case where marginal revenue collapses onto demand itself, since selling one more unit no longer costs the seller a lower price on every prior sale.

Close the unit in the sandbox. Hand a student the controls and let the class direct them: shift demand right, then lower marginal cost, then watch the profit rectangle and the deadweight loss triangle change shape together. Ask what happens to deadweight loss as marginal cost falls toward the socially optimal price. Student-driven and unscripted, so the questions the class asks reveal exactly what still has not landed.

The debrief question: why does perfect price discrimination erase the deadweight loss triangle even though the monopolist keeps all the surplus? The misconception it exposes: conflating deadweight loss with unfairness. The triangle measures trades that never happen, not who keeps the money from the trades that do.

Sequencing

A workable order across the unit: the auction to build the intuition that price is chosen, not given, the MR table race to make the arithmetic concrete, predict then reveal to correct the two most common drawing errors, the regulation debate and the natural monopoly case to apply the model to policy, and the sandbox and price discrimination close to tie profit, deadweight loss, and demand together on one graph. Compare each activity's outcome against what deadweight loss actually measures and against the perfect competition benchmark students already know, since the monopoly graph only makes sense next to the model it deviates from.

The monopoly module walks through the full graph step by step for students who need the model explained again after the activities, and full timings and materials for these and other market-structure activities are in the lesson plans.