See why cost-effective pollution control requires equating marginal abatement costs across firms, not uniform reductions
Combined baseline emissions: 100 units
Target: reduce by 60%
Baseline emissions: 50 units
Baseline emissions: 50 units
Cost-effectiveness requires MAC₁ = MAC₂.
With a uniform standard, the low-cost firm abates too little and the high-cost firm abates too much.
Tradeable permits (or firm-specific targets) achieve the same total reduction at lower cost by shifting abatement to the low-cost firm.