Skip to content

M16.L03 — Taxes and Subsidies in Consumer Theory

Module: Module 16 — Applications of Consumer Theory Lesson: L03 of 05 Duration: ~30 minutes Level: Intermediate Provenance: Principles of Microeconomics (Curtis and Irvine) | Khan Academy Microeconomics

Learning Objective

Compare the efficiency of different tax types using consumer theory.

Tax Effects on Budget Constraints

  1. Quantity Tax (e.g., GST): Rotates budget line inward
  2. Example: 10% GST on good x makes px → 1.1px

  3. Slope changes from -py/px to -py/(1.1px)

  4. Lump-Sum Tax: Parallel shift inward

  5. Reduces income but preserves relative prices

  6. More efficient (less utility loss per dollar raised)

  7. Income Tax: Similar to lump-sum but percentage-based

  8. Australian marginal rates: 19%-45%

Worked Example

Australian context: Compare two ways to raise $1000 revenue from a consumer with: - Income: $50,000 - Utility: U(x,y) = x^0.5 y^0.5 - Prices: px = $10, py = $20

  1. 10% GST on x: New px = $11 → Solve compensated demand DWL ≈ $120

  2. Lump-sum $1000: M = $49,000 → Less distortion DWL ≈ $0

Australia's GST raises ~\(75b/year vs income tax's ~\)250b (ATO 2022-23).

Common Misconception

"All taxes equally distort consumer choices"

Actually, lump-sum taxes (though politically unpopular) are theoretically most efficient as they don't alter relative prices.

Key Takeaways

  • Quantity taxes distort relative prices
  • Lump-sum taxes minimize deadweight loss
  • GST vs income tax involves equity-efficiency tradeoffs
  • Australian tax mix relies heavily on income taxes

Practice

  1. Derive the DWL formula for a quantity tax
  2. Calculate equivalent variation for 10% GST on x
  3. Graph Australian GST vs UK VAT (20%)

Further Resources

Provenance: Principles of Microeconomics (Curtis and Irvine) | Khan Academy Microeconomics