because the cheapest opportunities are likely to be exploited first absent other barriers abatement costs are minimised by the pricing of emissions this is all the more important at the international level where there are large differences in marginal abatement costs across countries the power of pricing to minimise abatement costs has been amply demonstrated in the united states through experience with the capandtrade scheme to reduce sulphur dioxide s emissions in the electricpower sector and hence acid rain introduced in it has resulted in almost a halving of these emissions and compliance costs are estimated to have been lower than would have been incurred had the command and control regulatory approaches considered by congress instead been adopted stavins and carlson et al