---
title: "Sherman Act | Principles of Economics"
description: "Sherman Act is the 1890 U.S. antitrust law banning restraints of trade and monopolization, a core Principles of Economics concept for market competition."
canonical: "https://fiveable.me/principles-econ/key-terms/sherman-act"
type: "key-term"
subject: "Principles of Economics"
unit: "Unit 11"
---

# Sherman Act | Principles of Economics

## Definition

The Sherman Act is the 1890 U.S. antitrust law that bans restraints of trade and attempts to monopolize markets. In Principles of Economics, it shows how government limits market power to protect competition.

## What It Is

The Sherman Act is the main federal antitrust law that comes up in Principles of Economics when you study competition, monopoly power, and government regulation of markets. Passed in 1890, it makes it illegal for firms to make agreements that restrain trade and to try to monopolize a market through anti-competitive conduct.

In simple terms, the law targets behavior that changes the way firms compete. Price fixing, market allocation, and other agreements between rivals can all fall under the Sherman Act because they replace competition with coordination. That matters in economics because competition is what usually pushes prices toward marginal cost, improves quality, and encourages innovation.

The act is not just about size. A firm can become very large without breaking the law if it grows through normal competition, better products, or lower costs. What triggers antitrust concern is the way power is used, especially when a company or group of companies blocks rivals, raises prices by reducing competition, or locks a market into a single dominant seller.

Economics classes often connect the Sherman Act to monopoly theory. A monopoly can charge higher prices and produce less than a competitive market, which creates deadweight loss. The law is one tool the government uses to stop firms from moving markets in that direction through collusion or exclusionary behavior.

You will also see the Sherman Act in merger discussions, even though the Clayton Act is the law that directly focuses on many proposed mergers. The Sherman Act still matters because a merger can create enough market power that the combined firm later behaves like a monopoly or engages in conduct meant to maintain dominance. That is why economists and regulators look at market structure, concentration, and actual behavior, not just whether a deal is labeled a merger.

## Why It Matters

The Sherman Act gives you a real-world way to connect abstract market models to policy. Perfect competition, monopoly, and oligopoly are not just graphs on a page. They help explain why the government steps in when firms coordinate prices, divide markets, or use power to shut out rivals.

In Principles of Economics, this term shows up whenever you ask, “What happens when competition breaks down?” If firms secretly agree to charge the same high price, consumers lose the benefits that competition is supposed to create. If one dominant company tries to keep rivals out, the market may stop behaving like the competitive model you study in class.

It also helps you separate legal market power from illegal conduct. A company can be big and still be lawful, but it cannot use certain strategies to preserve or expand monopoly power. That distinction shows up in case studies, policy questions, and merger discussions, especially when you compare market structure to market behavior.

The Sherman Act also gives you language for analyzing evidence. Instead of just saying a firm is “too powerful,” you can describe the specific behavior, such as price fixing, exclusionary contracts, or attempts to monopolize. That makes your economics explanations sharper and more accurate.

## Connections

### Antitrust Laws

The Sherman Act is one of the foundational antitrust laws, so it fits into the broader policy toolkit the government uses to protect competition. When a question asks about market regulation, antitrust laws are the wider category, while the Sherman Act is the specific law often tied to collusion and monopoly behavior.

### Monopoly

This term connects directly to monopoly because the Sherman Act targets attempts to monopolize markets and other behavior that protects monopoly power. In economics, a monopoly can set higher prices and produce less output than a competitive market, so the law is meant to stop firms from creating or preserving that outcome through unfair means.

### Merger

A merger is when two firms combine, and it can raise Sherman Act concerns if the new firm gains enough market power to reduce competition. In class, merger questions often ask whether a deal will lead to higher prices, less output, or fewer competitors. The Sherman Act is part of the legal background behind that analysis, even though merger review is often discussed with other laws too.

### [Clayton Act](/principles-econ/key-terms/clayton-act)

The Clayton Act and Sherman Act are often taught together, but they focus on different parts of antitrust enforcement. The Sherman Act handles restraints of trade and monopolization, while the Clayton Act targets specific practices, including mergers that may substantially lessen competition. That difference matters when you are deciding which law best fits a scenario.

## On the AP Exam

A quiz or problem-set question may give you a short market scenario and ask whether the Sherman Act applies. Your job is to identify the anti-competitive behavior, such as price fixing, collusion, or an attempt to monopolize, and explain how it affects competition, prices, and consumer choice. If a case study describes two firms secretly agreeing on prices, you should connect that to restrained trade, not just say “the market is bad.”

In a written response, use the term to explain the mechanism: how the conduct reduces competition and why that matters for efficiency and consumer welfare. If the prompt compares a merger with collusion, remember that the Sherman Act is about anti-competitive agreements and monopolization, while merger review usually brings in other antitrust rules too.

## Sherman Act vs Clayton Act

These are both antitrust laws, but they are not the same. The Sherman Act is the older law that bans restraints of trade and attempts to monopolize, while the Clayton Act is more specific and focuses on practices like mergers that may substantially lessen competition. If a question is about price fixing or collusion, Sherman Act is usually the better match; if it is about a proposed merger, Clayton Act is often the first law to consider.

## Key Takeaways

- The Sherman Act is the main federal antitrust law that bans restraints of trade and attempts to monopolize markets.
- In Principles of Economics, the law matters because it limits behavior that can reduce competition, raise prices, and lower consumer welfare.
- A firm can be large without violating the Sherman Act, but it can break the law if it uses anti-competitive agreements or exclusionary tactics.
- The term often appears in market structure lessons, monopoly analysis, and corporate merger discussions.
- When you see a scenario with price fixing, collusion, or monopoly maintenance, think Sherman Act first.

## FAQs

### What is the Sherman Act in Principles of Economics?

The Sherman Act is the federal antitrust law that bans restraints of trade and attempts to monopolize. In economics, it shows how the government tries to keep markets competitive when firms coordinate prices or use market power to block rivals. It is one of the main laws behind U.S. antitrust policy.

### What does the Sherman Act prohibit?

It prohibits contracts, combinations, or conspiracies that restrain trade, along with attempts to monopolize a market. That can include price fixing, market sharing, and other agreements that replace competition with coordination. The law focuses on conduct that harms competition, not just business size.

### How is the Sherman Act different from the Clayton Act?

The Sherman Act is broader and targets restraints of trade and monopolization. The Clayton Act is more specific and focuses on certain practices, including mergers that may substantially lessen competition. In an economics question, Sherman Act usually fits collusion or monopoly behavior, while Clayton Act often fits merger review.

### Can a monopoly violate the Sherman Act?

Yes, if it acquires or keeps its power through anti-competitive conduct. A company is not illegal just because it is big, but it can violate the Sherman Act by trying to monopolize a market or by using practices that shut out competitors. The law is about behavior, not size alone.

## Related Study Guides

- [11.1 Corporate Mergers](/principles-econ/unit-11/1-corporate-mergers/study-guide/dji0HMp6h49gtpBO)

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