Impostos sobre a gasolina ou sobre o automóvel?

A discussão não é tão simples. Afinal, existem carros mais eficientes no uso do combustível do que outros. Eis o que conclui este breve resumo de um estudo que usou dados da União Européia:

Our results show that EU consumers moderately undervalue future fuel costs. But this undervaluation is not enough to justify a strong emphasis on upfront car taxes. The car tax will result in a more fuel-efficient vehicle fleet than a fuel tax, but fails to target the high mileage consumers to drive with those more fuel efficient cars. Once we take this targeting effect into account, fuel taxes turn out to be a more effective instrument to reduce fuel usage (even if we assume that car usage is perfectly inelastic). When advising policymakers on the instruments to reduce externalities one should ask who is affected by the measure – will the heavy polluter change her choice?

Como eles fizeram isso? Dá uma lida lá.