AS & A-Level Economics — Government Intervention and Labour Markets

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Original Deckloop economics study material on government intervention and labour markets, with 120 practice cards and 24 concept explainers. Includes worked applications and analytical reasoning.

Economics EN A-Level

120 cards

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Specific vs. Ad Valorem Corrective Taxes

Corrective taxes, also known as Pigouvian taxes, are government interventions designed to internalise negative externalities. A specific tax is a fixed monetary amount levied per unit of a good or service. It shifts the supply curve vertically upwards by the exact tax amount, leading to a higher market price and lower quantity. An ad valorem tax, in contrast, is a percentage of the good's price. Its impact on the supply curve is a rotational shift, meaning the absolute tax amount per unit increases as the price of the good rises. Both types aim to reduce output towards the socially optimal level where marginal social cost equals marginal social benefit, by making producers or consumers bear the external cost. The choice between them can depend on how the external cost varies with output value.

Key points

Specific taxes are a fixed amount per unit, shifting supply vertically upwards by that amount.
Ad valorem taxes are a percentage of the price, causing the supply curve to pivot upwards.
Both types aim to internalise negative externalities, raising prices and reducing output.
Tax incidence (who bears the burden) depends on the relative price elasticities of demand and supply.

Worked example

Question

A local factory produces a chemical with a negative externality. The market demand for the chemical is P = 150 - 3Q, and the market supply is P = 30 + 2Q. The government determines that the marginal external cost is 15 monetary units per unit. Calculate the new market price and quantity if a specific corrective tax of 15 monetary units per unit is imposed.

Solution

1. Find the initial equilibrium without the tax:
2. 150 - 3Q = 30 + 2Q
3. 120 = 5Q
4. Q_initial = 24 units
5. P_initial = 150 - 3(24) = 150 - 72 = 78 monetary units
6. Apply the specific tax: A specific tax of 15 monetary units per unit means producers need to receive an additional 15 monetary units for each unit sold to cover the tax. This effectively shifts the supply curve upwards by 15 monetary units.
7. New supply equation: P_new_supply = (30 + 2Q) + 15 = 45 + 2Q
8. Find the new equilibrium with the tax:
9. 150 - 3Q = 45 + 2Q
10. 105 = 5Q
11. Q_new = 21 units
12. Calculate the new market price (consumer price):
13. P_new = 150 - 3(21) = 150 - 63 = 87 monetary units

After the specific corrective tax of 15 monetary units per unit, the new market quantity will be 21 units, and the new market price (paid by consumers) will be 87 monetary units.

Common pitfalls

Confusing specific and ad valorem taxes: A specific tax is a fixed amount per unit, while an ad valorem tax is a percentage of the good's value. Their impact on the supply curve's shape differs.
Assuming taxes always perfectly correct market failure: A corrective tax is only efficient if its rate equals the marginal external cost at the socially optimal output level, which requires accurate measurement and can be difficult to achieve.

Prerequisites

Deck 09 — Negative Production Externalities and Market Failure: Understanding negative externalities is essential as corrective taxes are designed to internalise these external costs, which is the core purpose explained in the summary and readiness check.
Deck 04 — Specific Taxes and the Price Wedge: This concept directly compares specific and ad valorem taxes, building upon the foundational understanding of how a specific tax (a fixed amount per unit) impacts supply and price, which is covered in this prerequisite.
Percentages and proportional change: Ad valorem taxes are defined as a percentage of the good's price, and their calculation in the worked example and card 2 requires an understanding of percentages.