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In page Carbon price:

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Carbon pricing is considered by many economists to be the most economically efficient way to reduce emissions,[1][2] taking into account the costs of both efficiency measures and the inconvenience of lesser fossil fuels. By pricing the externalities of carbon emissions, efficiency comes about by eliminating the market failure of the unpriced external costs of carbon emissions at its source.[3] It is regarded as more efficient than renewable energy subsidies given to individual firms,[citation needed] because the difficulties of determining the value of emissions to each firm makes command and control regulation less likely to be efficient.[4]