An environmental policy to raise the price of travel •(e.g. a national aviation tax) on a national or supra-national basis will be ineffective if the price elasticity of outbound travel is low, as found. A price inelastic response at the national or supra-national level means that the impact in terms of reducing demand will be proportionately less than the increase in price. The greater price sensitivity of inbound overseas residents will result in a diversion to other destinations, a “leakage of carbon”, and thus a reduction in environmental effectiveness.