How do you determine if a policy creates a deadweight loss?

How do you determine if a policy creates a deadweight loss?

• A. Determine DWL by tax revenue.
• B. DWL equals producer surplus.
• C. DWL is the rectangle between supply and demand curves.
• D. Compare social welfare at socially optimal quantity with welfare at policy outcome; DWL is the triangle between curves.

Answer: (D)

Deadweight loss shows up when a policy moves a market away from the quantity that would be socially efficient. In a competitive market, the efficient quantity is where marginal benefit equals marginal cost (the point where the demand and supply curves intersect). If a policy (like a tax, subsidy, price ceiling, or price floor) changes the outcome to a different quantity, total welfare falls compared with the efficient outcome. The DWL is the loss in total surplus relative to the welfare at the socially optimal quantity, and it shows up as a triangular area between the supply and demand curves from the actual quantity under the policy to the efficient quantity. The height of that triangle reflects the difference between marginal benefit and marginal cost at those quantities, and the base is the quantity gap. This is why comparing welfare at the efficient quantity to welfare at the policy outcome yields the DWL, and why it is represented as a triangle on a graph. Tax revenue by itself is not the DWL; DWL is the excess welfare loss not offset by any gains. The DWL is not the producer surplus, and it isn’t a rectangle between the curves—the triangle captures the lost mutually beneficial trades that no one compensates for under the policy.

Deadweight loss shows up when a policy moves a market away from the quantity that would be socially efficient. In a competitive market, the efficient quantity is where marginal benefit equals marginal cost (the point where the demand and supply curves intersect). If a policy (like a tax, subsidy, price ceiling, or price floor) changes the outcome to a different quantity, total welfare falls compared with the efficient outcome.

The DWL is the loss in total surplus relative to the welfare at the socially optimal quantity, and it shows up as a triangular area between the supply and demand curves from the actual quantity under the policy to the efficient quantity. The height of that triangle reflects the difference between marginal benefit and marginal cost at those quantities, and the base is the quantity gap. This is why comparing welfare at the efficient quantity to welfare at the policy outcome yields the DWL, and why it is represented as a triangle on a graph.

Tax revenue by itself is not the DWL; DWL is the excess welfare loss not offset by any gains. The DWL is not the producer surplus, and it isn’t a rectangle between the curves—the triangle captures the lost mutually beneficial trades that no one compensates for under the policy.