The larger the charge, the greater the percentage of pollutants any firm would be motivated to remove, though firms with low costs of control would remove larger percentages than would firms with high abatement costs.

• 收费越高，任何公司减少污染物百分比就越大，控制污染投入成本低的公司会比投入成本高的公司减少污染的百分比更大。