Chapter 11: Monopoly and Antitrust Policy
Antitrust laws are the rules society uses to keep markets competitive. When firms merge or engage in restrictive practices, regulators must decide whether the benefits (lower costs, greater efficiency) outweigh the risks (higher prices, less innovation). This chapter covers the tools for measuring market concentration, the types of anticompetitive behavior, the special challenges of natural monopolies, and the deregulation experiments of recent decades.
Table of Contents
Glossary at a Glance
| Term | Definition | |——|———–| | Merger | Two formerly separate firms combine into one | | Acquisition | One firm purchases another | | Antitrust laws | Laws giving government power to block mergers or break up large firms | | Four-firm concentration ratio | Combined market share of the four largest firms | | HHI | Sum of squared market shares of all firms in an industry | | Restrictive practices | Actions that reduce competition without explicit collusion | | Exclusive dealing | Agreement that a dealer sells only one manufacturer’s products | | Tying sales | Customer must buy a second product to get the first | | Bundling | Selling two or more products together as a package | | Predatory pricing | Cutting prices below cost to drive out competitors | | Natural monopoly | Market where one firm can serve all demand at lower cost than multiple firms | | Cost-plus regulation | Setting price = average cost + normal profit | | Price cap regulation | Setting a maximum price for several years ahead | | Regulatory capture | Regulated firms influence the regulations they face | | Deregulation | Removing government controls on prices and quantities |
1. Corporate Mergers & Antitrust Law
What Are Mergers and Acquisitions?
Merger: Two formerly separate firms combine to become a single firm. Acquisition: One firm purchases another (the acquired firm may keep its name). Both lead to two firms operating under common ownership.
- In a lateral merger, two firms of similar size combine
- Mergers above a minimum sales threshold ($101 million in 2022) must be reported to the Federal Trade Commission (FTC)
- Merger activity follows the business cycle — rising in booms, falling in recessions
The History of U.S. Antitrust Law
In the late 1800s, many U.S. industries were dominated by “trusts” — groups of formerly independent firms consolidated under common control. Congress responded with a series of landmark laws:
| Law | Year | Key Provision |
|---|---|---|
| Sherman Antitrust Act | 1890 | First antitrust law; banned monopolization and conspiracies in restraint of trade |
| Clayton Antitrust Act | 1914 | Outlawed mergers that “substantially lessen competition,” price discrimination, and tied sales |
| Federal Trade Commission | 1914 | Created the FTC to define and enforce fair competition |
| Celler-Kefauver Act | 1950 | Extended Clayton Act to restrict vertical and conglomerate mergers |
Standard Oil Breakup (1911): The Supreme Court upheld the government’s right to break up Standard Oil, which controlled ~90% of U.S. oil refining, into 34 independent firms — including Exxon, Mobil, Amoco, and Chevron.
When Is a Merger Approved?
The U.S. government approves most proposed mergers. In a market-oriented economy, firms have the freedom to expand, set prices, hire workers, and combine with other firms. The FTC itself notes: “Most mergers actually benefit competition and consumers by allowing firms to operate more efficiently.”
However, some mergers may lessen competition — leading to higher prices, lower quality, reduced innovation, or less availability of goods. Regulators may:
- Allow the merger outright
- Prohibit the merger
- Allow with conditions (e.g., the firm must sell off certain brands)
Johnson & Johnson / Pfizer Consumer Health (2006): Merger was approved on the condition that J&J sell off six brands — including Zantac, Cortizone, and Balmex — to preserve competition in those markets.
2. Measuring Market Concentration
Four-Firm Concentration Ratio
The four-firm concentration ratio is the combined market share of the four largest firms in an industry.
Formula:
\[CR_4 = s_1 + s_2 + s_3 + s_4\]where $s_i$ is the market share of the $i$-th largest firm.
Auto Windshield Replacement Market:
| Firm | Market Share |
|---|---|
| Smooth as Glass Repair Co. | 16% |
| The Auto Glass Doctor Co. | 10% |
| Your Car Shield Co. | 8% |
| Seven firms with 6% each | 42% combined |
| Eight firms with 3% each | 24% combined |
A $CR_4$ of 40 is not especially high — the top four firms hold less than half the market.
Interpreting the ratio:
- If two small firms merge → $CR_4$ unchanged → little competition concern
- If the top two firms merge → $CR_4$ rises to $26 + 8 + 6 + 6 = 46$ → still modest
Herfindahl-Hirschman Index (HHI)
The four-firm ratio has a weakness: it doesn’t distinguish between industries where the top 4 firms each have 20% vs. one firm having 77% and others 1% each. The HHI fixes this.
Herfindahl-Hirschman Index (HHI): Sum of the squares of every firm’s market share.
\(HHI = \sum_{i=1}^{N} s_i^2\)
Key benchmarks:
- Pure monopoly (100% share): $HHI = 100^2 = 10{,}000$
- Highly competitive (100 firms × 1% each): $HHI = 100 \times 1^2 = 100$
- Windshield market: $HHI = 16^2 + 10^2 + 8^2 + 7(6^2) + 8(3^2) = 744$
Why HHI is better than $CR_4$: Two industries both have $CR_4 = 80$. But:
- Industry A: 5 firms × 20% each → $HHI = 5(20^2) = 2{,}000$
- Industry B: 1 firm at 77% + 23 firms at 1% → $HHI = 77^2 + 23(1^2) = 5{,}952$
HHI reveals that Industry B is far more concentrated — essentially a near-monopoly.
FTC Guidelines (1980s):
| HHI After Merger | FTC Response |
|---|---|
| Below 1,000 | Probably approved |
| 1,000 – 1,800 | Scrutinized case-by-case |
| Above 1,800 | Probably challenged |
Real-World Examples (2016):
| U.S. Industry | $CR_4$ | HHI |
|---|---|---|
| Wireless | 98 | 2,736 |
| Personal Computers | 76 | 1,234 |
| Airlines | 69 | 1,382 |
| Automobiles | 58 | 1,099 |
New Directions for Antitrust
Both $CR_4$ and HHI have weaknesses:
- They assume the “market” is well-defined — but market definition is often controversial
- They assume competitive conditions are similar across industries
Market definition matters enormously. Microsoft in the early 2000s had a dominant share of OS software — but only ~14% of all computer software and services. A narrow market definition makes concentration look high; a broad definition makes it look low.
Two forces have reshaped market definitions:
- Technology: The internet lets consumers buy from anywhere, increasing competition for local businesses
- Globalization: U.S. automakers’ share fell below 50% by 2014 as foreign competitors entered
The FTC has moved toward case-by-case analysis — estimating demand and supply curves, modeling how competition actually works in a specific industry, rather than relying on simple ratios.
Whole Foods / Wild Oats (2007): The FTC looked at detailed evidence on prices and profits for specific stores in different cities, rather than just computing market shares. After two years of legal battles, the merger was allowed in 2009 under conditions that Whole Foods sell off the Wild Oats brand name and several individual stores.
3. Regulating Anticompetitive Behavior
Under U.S. law, monopoly itself is not illegal. A firm can earn high profits through a new patent or by producing a better product at a lower price. What is illegal is using market power to engage in anticompetitive practices.
Cartels and Price Fixing
The FTC and DOJ prohibit firms from agreeing to:
- Fix prices or output
- Rig bids
- Divide markets by allocating customers, suppliers, or territories
International Vitamin Cartel (1990s): Hoffmann-La Roche (Swiss), BASF (German), and Rhône-Poulenc (French) agreed on how much to produce, what to charge, and which firm would sell to which customers. Companies like General Mills, Kellogg, and Procter & Gamble paid inflated prices. Hoffmann-La Roche pled guilty, paid a $500 million fine, and its top executive was incarcerated for four months.
Restrictive Practices
Restrictive practices reduce competition without outright agreements to fix prices. They are often controversial because the same practice can be legal in one context and illegal in another.
| Practice | Description | Legal When… | Illegal When… |
|---|---|---|---|
| Exclusive dealing | Dealer sells only one manufacturer’s products | Encourages inter-brand competition (e.g., Ford dealers sell only Ford) | One retailer gets exclusive rights to multiple brands, blocking competitors |
| Tying sales | Must buy Product B to get Product A | Products are naturally related | Forces consumers to buy unwanted products |
| Bundling | Two+ products sold as a package | Gives consumers a better price (e.g., cable + internet bundle) | Customers cannot buy products separately |
| Predatory pricing | Selling below average variable cost to drive out competitors | Firm is simply matching a competitor’s price | Firm deliberately underprices to eliminate competition, then raises prices |
Predatory pricing is hard to prove. If American Airlines cuts fares to match a new entrant, is it predatory pricing or normal competition? The common test: a firm selling below its average variable cost is evidence of predatory intent — but calculating real-world variable costs is rarely straightforward.
The Microsoft Case
Microsoft Antitrust Case (1990s–2002):
- Microsoft’s Windows had a near-monopoly in PC operating systems
- Government alleged Microsoft used its OS monopoly to take over other software markets:
- Exclusive dealing: Threatened PC makers that refused to remove Netscape’s browser
- Tying sales: Bundled Internet Explorer with Windows
- Predatory pricing: Gave away free software to drive out competitors
- In April 2000, a federal court ruled Microsoft had engaged in unfair competition and recommended splitting it in two
- On appeal, the breakup was overturned; Microsoft settled in November 2002, agreeing to end restrictive practices
4. Regulating Natural Monopolies
A natural monopoly arises when average costs decline over the range of production that satisfies market demand — typically because fixed costs are large relative to variable costs. One firm can serve the whole market at lower cost than two or more firms could.
Examples: Water utilities, electricity providers, (historically) landline telephone service
Four Regulatory Options
Consider a natural monopoly with the following data:
| Q | Price | TR | MR | TC | MC | AC |
|---|---|---|---|---|---|---|
| 1 | 14.7 | 14.7 | 14.7 | 11.0 | — | 11.00 |
| 2 | 12.4 | 24.7 | 10.0 | 19.5 | 8.5 | 9.75 |
| 3 | 10.6 | 31.7 | 7.0 | 25.5 | 6.0 | 8.50 |
| 4 | 9.3 | 37.2 | 5.5 | 31.0 | 5.5 | 7.75 |
| 5 | 8.0 | 40.0 | 2.8 | 35.0 | 4.0 | 7.00 |
| 6 | 6.5 | 39.0 | −1.0 | 39.0 | 4.0 | 6.50 |
| 7 | 5.0 | 35.0 | −4.0 | 42.0 | 3.0 | 6.00 |
| 8 | 3.5 | 28.0 | −7.0 | 45.5 | 3.5 | 5.70 |
| 9 | 2.0 | 18.0 | −10.0 | 49.5 | 4.0 | 5.50 |
Four choices for regulators:
| Option | Point | Q | P | Result | |——–|——-|—|——|——–| | A. Unregulated monopoly | MR = MC | 4 | 9.30 | Earns economic profit (P > AC = 7.75) | | B. Break up the firm | Split in two | 2 each | 9.75 | Higher AC → less productive efficiency | | C. Price = MC | MC = Demand | 8 | 3.50 | Allocatively efficient but P < AC (5.70) → firm loses money | | F. Price = AC | AC = Demand | 6 | 6.50 | Zero economic profit; firm survives; most practical |
- Option A (do nothing): Monopoly produces too little at too high a price
- Option B (split up): With declining AC, two smaller firms always have higher costs → wasteful
- Option C (P = MC): Ideal for allocative efficiency, but P < AC means losses → requires government subsidy
- Option F (P = AC): Best practical choice — covers costs, earns normal profit, prevents monopoly pricing
Diagram — Natural Monopoly Regulation Options:
Cost-Plus vs. Price Cap Regulation
| Approach | How It Works | Advantage | Disadvantage |
|---|---|---|---|
| Cost-plus regulation | Regulator allows firm to cover all costs + normal profit | Firm won’t go bankrupt | No incentive to cut costs; may inflate costs |
| Price cap regulation | Regulator sets a maximum price for several years (often declining) | Incentive to cut costs → keep extra profit | If cap is too low, firm may fail; doesn’t adapt to sudden cost shocks |
The cost-plus problem: If a firm gets reimbursed for whatever it spends plus a profit margin, it has every incentive to build lavish facilities and hire excess staff — because higher costs mean higher revenue.
Modern Antitrust: The Google Case (2020–2024)
U.S. v. Google LLC (2020):
The DOJ filed its largest antitrust case since Microsoft, alleging Google maintained an illegal monopoly in search and search advertising:
| Metric | Google’s Position |
|---|---|
| U.S. search market share | ~90% |
| Payments to Apple to be default search on Safari | ~$26 billion/year (2021) |
| Share of search advertising revenue | ~92% |
The antitrust argument: Google pays billions to be the default search engine on browsers and phones, foreclosing competitors from distribution channels. This makes it nearly impossible for rivals (Bing, DuckDuckGo) to reach scale.
August 2024 ruling: Federal Judge Mehta found Google guilty of maintaining an illegal monopoly in general search. Remedies (potentially including a breakup or ban on default agreements) are still being determined.
This case updates the Microsoft precedent for the age of platform monopolies.
5. The Great Deregulation Experiment
The Push for Deregulation
Beginning in the 1970s, the U.S. carried out a major policy experiment — deregulating industries where government had controlled prices and quantities:
- Airlines (1978)
- Railroads
- Trucking
- Intercity bus travel
- Natural gas
- Bank interest rates
Airline Deregulation (1978):
- Before: The Civil Aeronautics Board (CAB) controlled all fares, routes, and entry for 40 years (1938–1978). Zero new airlines entered major routes.
- After: Air fares fell by ~one-third over two decades. Average flight occupancy rose from 50% to 67%. Airlines developed hub-and-spoke systems for greater coverage. Passenger numbers doubled from the late 1970s to 2000s, doubling airline jobs. Safety continued to improve.
- Downside: Famous airlines (Pan Am, Eastern, Braniff) went bankrupt. New entrants (People Express) appeared and vanished. Recent mergers have raised competition concerns.
Regulatory Capture
Regulatory capture occurs when the firms supposedly being regulated end up playing a large role in setting the very regulations they follow. Regulated firms suggest appointees to regulatory boards, lobby intensively, provide most of the information for decisions, and offer well-paid jobs to departing regulators.
The result: regulation becomes a tool for existing competitors to restrict entry, keep prices high, and limit competition — the opposite of its intended purpose.
Post-Deregulation Challenges
Deregulation also had side effects:
- Major accounting scandals (Enron, Tyco, WorldCom) → Sarbanes-Oxley Act (2002) to protect investors
- Unregulated financial products (CMOs, CDSs) contributed to the Great Recession (2007–2009) → Dodd-Frank Act to reform the financial system and end “too big to fail”
The balancing act: All market economies operate within a framework of laws. The challenge is finding the right level of regulation — enough to prevent monopoly abuse and financial crises, but not so much that it stifles competition and innovation.
6. Key Takeaways
- Antitrust laws (Sherman, Clayton, FTC) prevent mergers and practices that would substantially reduce competition
- The four-firm concentration ratio ($CR_4$) gives a quick snapshot but doesn’t capture distribution of market share
- The HHI (sum of squared shares) better reveals whether one firm dominates; FTC uses thresholds of 1,000 and 1,800
- Market definition is crucial and controversial — technology and globalization have broadened many markets
- Restrictive practices (exclusive dealing, tying, bundling, predatory pricing) can be legal or illegal depending on context
- Natural monopolies have declining AC — breaking them up raises costs, so regulation (not competition) is needed
- Price = AC (Option F) is the most practical regulatory choice for natural monopolies
- Cost-plus regulation guarantees survival but kills efficiency incentives; price cap regulation creates incentives but requires careful calibration
- Deregulation of airlines, trucking, and other industries brought lower prices and more service, but also disruption
- Regulatory capture turns regulation into a tool for incumbents — a key argument for deregulation
7. Glossary
| Term | Definition |
|---|---|
| Acquisition | One firm purchases another |
| Antitrust laws | Laws giving government power to block mergers or break up large firms to preserve competition |
| Bundling | Selling two or more products together as one package |
| Celler-Kefauver Act | 1950 law extending Clayton Act to restrict vertical and conglomerate mergers |
| Clayton Antitrust Act | 1914 law outlawing anticompetitive mergers, price discrimination, and tied sales |
| Concentration ratio | Combined market share of the largest firms (typically top 4) |
| Cost-plus regulation | Setting price to cover costs plus a normal rate of profit |
| Deregulation | Removing government controls on prices and quantities produced |
| Exclusive dealing | Agreement that a dealer sells only one manufacturer’s products |
| HHI | Sum of squared market shares; ranges from near 0 (perfect competition) to 10,000 (pure monopoly) |
| Market share | A firm’s percentage of total industry sales |
| Merger | Two formerly separate firms combine into a single firm |
| Natural monopoly | Industry where declining AC means one firm serves all demand at lower cost |
| Predatory pricing | Selling below cost to drive competitors out, then raising prices |
| Price cap regulation | Regulator sets a maximum price for a multi-year period |
| Regulatory capture | Regulated firms influence the rules they’re supposed to follow |
| Restrictive practices | Actions that reduce competition without outright collusion |
| Sherman Antitrust Act | 1890 — the nation’s first antitrust law |
| Tying sales | Customer must purchase a second product in order to buy the first |
8. Practice Questions
Q1. What is the difference between a merger and an acquisition?
A: A merger combines two separate firms into one new entity (often of similar size). An acquisition is when one firm purchases another. Both result in two previously independent firms operating under common ownership.
Q2. An industry has four firms with market shares of 30%, 25%, 20%, and 10%, plus 15% split among small firms. What is the four-firm concentration ratio?
A: $CR_4 = 30 + 25 + 20 + 10 = 85$. This is a highly concentrated market — the top four firms control 85% of sales.
Q3. Calculate the HHI for an industry with five firms holding 40%, 20%, 15%, 15%, and 10% of the market.
A: $HHI = 40^2 + 20^2 + 15^2 + 15^2 + 10^2 = 1{,}600 + 400 + 225 + 225 + 100 = 2{,}550$. Under 1980s FTC guidelines, this would likely be challenged (above 1,800).
Q4. Two industries both have a four-firm concentration ratio of 80. In Industry A, four firms each have 20%. In Industry B, one firm has 74% and six firms each have 1%. Which industry is more concentrated? How does the HHI reveal this?
A: Industry B is far more concentrated. HHI for A = $4(20^2) = 1{,}600$. HHI for B = $74^2 + 6(1^2) = 5{,}476 + 6 = 5{,}482$. The HHI reveals the near-monopoly in Industry B that the $CR_4$ conceals.
Q5. Why is market definition important in antitrust analysis? Give an example.
A: A narrowly defined market makes concentration appear high; a broadly defined market makes it appear low. Microsoft had a dominant share of “PC operating systems” but only ~14% of “all computer software and services.” Whether a merger raises competition concerns depends heavily on how broadly or narrowly the market is defined.
Q6. What is the difference between tying sales and bundling?
A: In tying sales, a customer is forced to buy a second product in order to get the first — and cannot buy them separately. In bundling, two or more products are offered together at a better price, but customers can typically still buy them individually. Tying is generally more anticompetitive.
Q7. Why is predatory pricing difficult to prove in practice?
A: It’s hard to distinguish between a firm legitimately matching a competitor’s lower price and a firm deliberately pricing below cost to drive competitors out. The common test is whether the firm sells below its average variable cost, but calculating variable costs in the real world is rarely straightforward.
Q8. Why would breaking up a natural monopoly into competing firms be counterproductive?
A: A natural monopoly has declining average costs over the relevant range of output. If the firm is split in two, each half produces at a higher point on the AC curve — meaning higher average costs, less productive efficiency, and ultimately higher prices for consumers. Additionally, one firm may eventually drive the other out due to its cost advantage, recreating the monopoly.
Q9. Using the natural monopoly data in this chapter, what is the monopoly price and quantity? What about the allocatively efficient price and quantity?
A: Monopoly: MR = MC at Q = 4, P = 9.30 (Point A). Allocatively efficient: P = MC at Q = 8, P = 3.50 (Point C). However, at Point C, price (3.50) < AC (5.70), so the firm would need a subsidy of $(5.70 − 3.50) \times 8 = $17.60$ to survive.
Q10. Compare cost-plus regulation and price cap regulation. Which provides better incentives for efficiency?
A: Cost-plus lets the firm charge enough to cover all costs plus a normal profit — but this removes the incentive to cut costs (or even encourages inflating them). Price cap sets a maximum price for several years — if the firm cuts costs below the cap, it earns extra profit, creating a strong efficiency incentive. Price cap regulation provides better incentives, but risks are higher if the cap is set too low.
Q11. What is regulatory capture? Why does it weaken the argument for government regulation?
A: Regulatory capture occurs when regulated firms influence the regulatory process — by suggesting appointees, lobbying, providing biased information, and offering jobs to departing regulators. Instead of protecting consumers, regulation becomes a tool for incumbents to restrict entry and keep prices high, undermining its entire purpose.
Q12. Describe three results of airline deregulation in the United States.
A: (1) Air fares fell by approximately one-third over two decades, saving consumers billions per year. (2) Airlines developed hub-and-spoke systems, providing service to more cities with just one connection. (3) Passenger numbers doubled from the late 1970s to 2000s, doubling airline industry jobs. On the negative side, established airlines like Pan Am, Eastern, and Braniff went bankrupt.