6.4

The Effects of Government Intervention in Markets

AP Microeconomics

Why Government Intervenes

Taxes to Correct Negative Externalities

Subsidies to Correct Positive Externalities

Regulation of Natural Monopolies

Unregulated Monopoly $MR = MC$ → low Q, high P, DWL

Socially Optimal Pricing ($P = MC$) Allocatively efficient but firm earns a **loss** (P < ATC) → requires government subsidy

Fair-Return Pricing ($P = ATC$) Firm earns **zero economic profit** → no subsidy needed, but some DWL remains ($P > MC$)

12345678910111234567891011121314151617181920Quantity$/unitFair return (P=ATC)Socially optimal (P=MC)ATCMCD

Natural monopoly: P=ATC earns zero profit; P=MC is efficient but firm loses money

Antitrust Policy

Tradable Pollution Permits (Cap and Trade)

Government Provision of Public Goods

Price Controls (Review)

Unintended Consequences

AP Exam Tips

Common Mistakes