It is well-known that economic instruments like taxes and tradable permits can improve the efficiency of attaining a target expressed in terms of a single variable, but many energy and environmental regulations are expressed as a ratio of two variables, for instance, as emissions intensity (tons per unit output) or as a renewables requirement (percentage from wind, biomass, etc.). It has been shown previously that conventional formulas for cost-efficiency do not work in this case. This paper shows that even if conventional permit trading is used, the cost-effective implementation is unlikely to be achieved. Alternative rules are presented that permit decentralized market-based implementation of ratio standards to achieve a cost-effective implementation of a ratio standard.