How do cap-and-trade programs reduce pollution?

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Cap-and-trade uses a cap on emissions and permit trading to achieve reductions at the lowest cost. By setting an overall limit on how much pollution can be emitted, the program guarantees a specific environmental outcome. Each emitter receives or can buy permits that authorize a certain amount of emissions, and they must hold enough permits to cover their actual emissions. Because permits can be bought and sold, firms with very low abatement costs can reduce more than required and sell their extra permits, while firms facing higher costs can meet their obligations by purchasing permits instead of making expensive reductions. This creates a market price for emitting and steers pollution reductions toward the most cost-effective opportunities, all while the total emissions stay within the cap. Over time, tightening the cap amplifies environmental benefits and pushes ongoing innovation in cleaner processes and technologies.

The other ideas don’t fit because a cap-and-trade system is not about banning emissions outright, nor about boosting fossil fuel subsidies, and it targets more than just water pollution—it's designed to limit overall emissions, typically of air pollutants or greenhouse gases, with flexibility to meet that limit at lower costs.