Market Power II:
Addressing Market Power
Where power comes from — and whether the cure can be trusted
The last chapter ended on a question it refused to answer. A monopolist can restrict output or, by sorting buyers, expand it. Either way it has power. But where did the power come from?
Picture two firms with the same fat profit. The first earned it by building something rivals can't yet match, and it knows the clock is ticking: someone is in a garage right now trying to take it away. The second earned it by securing a license only it can hold, a tariff that prices out foreign rivals, or a regulation it helped write. Its profit isn't a prize for being better. It's a wall, and the firm spends real money keeping the wall standing.
Both show up in the data as “market power.” Only one is the kind a competitive economy is supposed to produce. This chapter is about telling them apart — and about why the obvious cure, send in the government, is harder than it sounds when the government is so often where the wall came from.
Where Durable Power Comes From
Every lasting monopoly is protected by something. The question is by what.
A loss as visible as monopoly — high price, restricted output, fat profit — should invite rivals. They flood in, compete the price down, and the profit evaporates. So when market power lasts, something is holding the door shut. That something is a barrier to entry, and barriers are the difference between a firm that is merely successful and one that is durably powerful.
Not all barriers are alike, and the differences are the whole moral of the chapter. Some are earned: a genuinely lower cost structure, a patent on an invention that didn't exist before, a product so good that users pull in other users. Others are erected: a license only incumbents can get, a rule written to be expensive for newcomers to satisfy, a tariff that fences out foreign rivals. The economist Schumpeter insisted that much market power is the temporary prize of innovation — a reward the next innovator is already racing to take away. He was often right. But “often” is not “always,” and the barriers that don't erode are usually the ones someone built on purpose.
| Source of power | Type | Does it tend to erode on its own? |
|---|---|---|
| Economies of scale (natural monopoly) | Earned / structural | No — but it may be genuinely cheaper for one firm to serve all. |
| A better product; network effects from real adoption | Earned | Often — a better rival can flip the network. |
| Patents and intellectual property | Legal, time-limited | Yes, by design — protection expires. |
| Occupational licensing, permits, quotas | Erected / legal | No — rules persist until repealed. |
| Tariffs and import restrictions | Erected / legal | No — they fence out rivals indefinitely. |
| Control of a key resource | Mixed | Sometimes — substitutes and new sources appear. |
Quick checkTwo firms each hold 80% of their market. One's share keeps slipping as rivals improve; the other's hasn't moved in 30 years behind a licensing rule. Which has the more worrying power?▸
Power Made by Policy
The cheapest way to beat your competitors is sometimes to change the rules so they can't compete.
Here is the turn the standard story misses. We tend to imagine monopoly arising in the market and government arriving afterward to fix it. But a great deal of durable power is created by government in the first place — through licenses, permits, quotas, tariffs, zoning, and regulations that happen to be easy for incumbents and expensive for entrants. When a firm helps shape the rules it operates under, the result is regulatory capture, and the wall it produces does not erode, because erosion would require the rule-makers to act against the people who benefit.
Why would a firm do this rather than just compete? Because it pays. Effort spent winning a protected position is called rent-seeking, and it has a cost the textbook monopoly diagram hides. Recall the deadweight-loss triangle: the trades that never happen. The economist Tullock pointed out that the monopoly profit rectangle — which the basic model treats as a harmless transfer from buyers to the firm — is not harmless if firms burn real resources fighting over it. Lawyers, lobbyists, campaign donations, duplicated effort to defend the moat: all of that is labor and capital that produces nothing. In the limit, the entire rectangle can be dissipated into waste. The social cost of protected monopoly is then not just the triangle, but the triangle plus much of the rectangle.
This is not a left-wing idea or a right-wing idea. It is one of the rare places they meet. Acemoglu and the institutional tradition argue that the central economic question is whether a society's rules are inclusive or extractive — whether power is open to challenge or rigged to protect insiders. The public-choice tradition, coming from the libertarian right, argues that government actors respond to incentives just like everyone else, so rules get captured by the organized few at the expense of the dispersed many.
Different politics, same diagnosis: captured rules create durable, costly power. They part ways only on the cure — one trusts better institutions and oversight, the other trusts smaller targets for capture. When two traditions this far apart agree on what the disease is, the diagnosis is worth taking seriously.
Retrieval practiceExplain why a $1 million monopoly profit might cost society more than $1 million.▸
The deadweight-loss triangle is already a loss on top of the profit. And if firms spend real resources — lobbying, legal fees, duplicated effort — competing to win and defend that $1 million, those resources produce nothing of value. The profit that looked like a pure transfer becomes, in part or in whole, wasted effort. So the social cost is the triangle plus the rent that gets dissipated.
Natural Monopoly and the Regulator's Dilemma
Sometimes one firm really is cheapest — and that is exactly when regulating it gets hard.
Not all monopoly is manufactured. Sometimes a single firm genuinely can serve a whole market at lower average cost than several could, because the fixed cost is enormous and the cost of one more unit is tiny: water mains, the electric grid, rail track, pipelines. This is a natural monopoly, and duplicating its infrastructure to “create competition” would just waste money. Here the problem isn't that the firm shouldn't exist. It's that, left alone, it will price like any monopolist — restrict output, raise price — on infrastructure everyone needs.
So regulators try to set the price. And immediately they hit a dilemma that has no clean answer, because the firm's average total cost is still falling across the whole market.
| Remedy | What it does | The catch |
|---|---|---|
| Marginal-cost pricing (P = MC) | Efficient output | Firm loses money; needs an ongoing subsidy. |
| Average-cost / fair-return (P = ATC) | Firm breaks even | Output still below efficient; little incentive to cut costs. |
| Price-cap regulation | Rewards cost-cutting | Set the cap wrong and you get shortages or windfalls. |
| Public ownership | Removes the profit motive to restrict | May lose the discipline that keeps costs down. |
| Franchise bidding | Competition for the market | Hard to write and enforce a long-run contract. |
Quick checkWhy can't a regulator just order a natural monopoly to charge P = MC and be done?▸
Antitrust, the Contested Remedy
The tool we reach for to fix market power is itself a judgment call — and it can miss in both directions.
When power comes from conduct rather than from a captured rule, the classic remedy is antitrust: laws that block price-fixing, stop mergers that would lessen competition, and forbid tactics designed to exclude rivals rather than to win customers. At its best, antitrust does for the market what nothing else can — it keeps the field open. But it is contested for honest reasons, not just political ones.
The first difficulty is defining the market. A firm looks dominant or harmless depending on where you draw the boundary, and reasonable analysts draw it differently. The second is the error problem. Enforcers can make two kinds of mistake: punish a firm that simply won by serving customers better (a false positive that chills the very competition we want), or wave through real entrenchment (a false negative that lets a wall harden). The third is the deepest, and it brings the chapter full circle: antitrust is run by government, and government is capturable. The agency meant to police market power can be lobbied, staffed, and steered by the firms it polices.
Misconception“Antitrust exists to punish companies for being big.”▸
Size won by serving customers is not the target — in fact, punishing it would discourage exactly the competition that benefits buyers. The target is conduct and barriers that block rivals from competing: collusion, mergers that remove a real competitor, tactics meant to exclude rather than to win. The chapter's whole distinction returns here: the issue is never bigness, it's protected power.
Retrieval practiceGive one reason antitrust is genuinely hard, beyond politics.▸
Any one of: the market is hard to define, so dominance is in the eye of the beholder; enforcers can err by punishing earned success or by missing real entrenchment; or the enforcing agency can itself be captured by the firms it is meant to police.
The moves you can now make
Honest heads-up: of this chapter, only natural-monopoly regulation is heavily AP-tested. Sources, rent-seeking, and antitrust are conceptual — tested in reasoning, not graphs.
Identify and explain
Classify each barrier as more likely to erode on its own or to persist until repealed: (i) a network effect, (ii) an occupational license, (iii) a 20-year patent, (iv) an import tariff.
Reveal answer▸
Erode on their own: (i) a network effect can flip if a better rival attracts users; (iii) a patent expires by design. Persist until repealed: (ii) an occupational license and (iv) a tariff are erected rules that don't erode through competition — only through politics.
Welfare reasoning
Explain why the social cost of a politically protected monopoly can exceed the deadweight-loss triangle.
Reveal answer▸
The triangle is the lost trades. On top of it, firms spend real resources — lobbying, legal effort, duplicated defense of the moat — to win and keep the monopoly profit. That rent-seeking turns the profit rectangle, a mere transfer in the basic model, into wasted resources. Cost = triangle + dissipated rent.
Graph reasoning
On a natural-monopoly graph, why does marginal-cost pricing force a loss, and what does fair-return pricing trade away to avoid it?
Reveal answer▸
Because ATC is falling, MC lies below ATC. Setting P = MC puts price below average cost, so the firm loses money and needs a subsidy. Fair-return pricing sets P = ATC so the firm breaks even — but that price is above MC, so output stays below the efficient level. You trade efficiency for solvency.
Regulating a natural monopoly
A natural monopoly faces downward-sloping demand. Its average total cost is falling throughout the relevant range, so marginal cost lies below average total cost.
- Draw a correctly labeled graph with D, MR, MC, and a falling ATC. 1 pt
- Identify the unregulated price and quantity. 1 pt
- Identify the allocatively efficient quantity (P = MC). 1 pt
- Explain why the firm earns a loss at the allocatively efficient price. 1 pt
- Identify the fair-return price and quantity (P = ATC). 1 pt
- Explain what fair-return pricing trades away relative to P = MC. 1 pt
- Define rent-seeking. 1 pt
- Explain why rent-seeking can make a protected monopoly more costly than the deadweight-loss triangle alone. 1 pt
- Explain one reason regulation may fail to fix the problem. 1 pt
Reveal scoring guide▸
- 1 ptD, MR, MC, and a downward-sloping ATC with MC below ATC.
- 1 ptUnregulated Q at MR = MC; price read up on demand.
- 1 ptEfficient Q where D = MC.
- 1 ptAt P = MC, price is below ATC (because ATC is falling), so the firm makes a loss.
- 1 ptFair-return Q where D = ATC; price = ATC.
- 1 ptFair-return output is below the efficient quantity, so some efficient trades are still lost.
- 1 ptRent-seeking is spending real resources to win or defend a protected profit rather than to create value.
- 1 ptResources spent fighting over the profit rectangle are wasted, adding to the triangle's loss.
- 1 ptAny valid reason: regulatory capture, hard-to-define markets, enforcement errors, or weak cost-cutting incentives under fair-return pricing.
Market power is as often manufactured through politics as it is won in the market — and that makes the cure harder than the diagnosis.
they would spend less effort breaking up big firms and more repealing the rules that manufacture them — every needless license, tariff, and captured regulation that quietly turns public power into private rent.
- Durable power requires a barrier; barriers that don't erode are usually erected.
- Rent-seeking can dissipate the profit rectangle, so protected monopoly can cost more than the triangle.
- A natural monopoly poses a real dilemma: P = MC is efficient but loss-making; P = ATC breaks even but isn't efficient.
- Which barriers are worth their cost — which patents, which licenses, which scale?
- Are antitrust's errors — chilling success vs. missing entrenchment — worth its wins?
- Who regulates a regulator that can be captured?
When a price stays high and no new rival shows up to undercut it, ask what's keeping competitors out — and whether it's a rule someone lobbied for rather than a product no one can match.
Know which kind of moat you have. One built on serving customers better erodes the moment you stop; one built on a friendly rule erodes the moment the politics shift. They demand very different strategies.
