Consider a market where the production of a good generates a negative externality, such as pollution that harms a nearby community. This market can be visualized on a graph with 'Price/Cost' on the vertical axis and 'Quantity' on the horizontal. The graph features an upward-sloping Marginal Private Cost (MPC) curve and a higher upward-sloping Marginal Social Cost (MSC) curve. A horizontal line represents the constant market Price. The unregulated market produces at quantity Q_A, corresponding to point A where the Price line intersects the MPC curve. The socially optimal production level is at quantity Q_B, corresponding to point B where the Price line intersects the MSC curve. Point C is the point on the MPC curve that is vertically below point B. Point D is the point on the MSC curve that is vertically above point A.

If a policy is enacted that reduces the quantity produced from the market level (Q_A) down to the socially optimal level (Q_B), which geometric area represents the total gain for the community that was previously being harmed by the pollution?

Calculating External Cost Reduction

Explaining the Gain from Correcting an Externality

Welfare Analysis of Externality Correction

Consider a market where production creates a negative externality. The diagram for this market shows 'Quantity' on the horizontal axis and 'Price/Cost' on the vertical. It includes a horizontal market price line (P*), an upward-sloping Marginal Private Cost (MPC) curve, and a higher upward-sloping Marginal Social Cost (MSC) curve. The unregulated market produces at quantity Q_m (where P* intersects MPC), while the socially efficient quantity is Q_s (where P* intersects MSC). Match each economic concept below with the geometric area on the diagram that represents it, assuming output is reduced from Q_m to Q_s.

Consider a market where the production of a good imposes a negative external cost on a third party. On a diagram representing this market, the Marginal Social Cost (MSC) curve lies above the Marginal Private Cost (MPC) curve. Production is initially at the privately optimal quantity (where Price = MPC), but a policy is implemented to reduce output to the socially efficient quantity (where Price = MSC).

True or False: The total reduction in external costs experienced by the third party (their total gain) is exactly equal to the total loss of profit experienced by the producers as a result of this output reduction.

Calculating Welfare Gains from Externality Correction

Consider a market where production imposes costs on a third party. On a standard diagram for this market, the vertical distance between the Marginal Social Cost (MSC) curve and the Marginal Private Cost (MPC) curve represents the marginal external cost at any given quantity. When a policy reduces production from the inefficient, privately-optimal quantity to the socially-optimal quantity, the total gain for the third party is represented by the area between the MSC and MPC curves, bounded by these two quantities. This area is therefore the sum of the __________ for each unit of output that is eliminated.

Evaluating Competing Claims on Externality Correction

Calculating the Reduction in External Costs

Net Social Gain from Moving to a Pareto-Efficient Outcome