Reply to A. Collins

The author puts forward various points which in a sense we would not disagree with. However, the main thrust of the Comment is a concern for the focus of the paper. He does not actually disagree with the content of the paper, but implies a different emphasis. ld draw attention in particular to the last paragraph in our Introduction, which clearly states the scope and boundaries of the paper: the potential of permit systems that is to be considered” political problems of international cooperation are present, and this is true no matter which policy instrument is being considered when gainers and losers are involved” likewise there will always be monitoring and enforcement costs under any regulatory system” nally “whilst the significance of these issues should not be under-estimated in the context of practical policy design, they are not the focus of this paper”. explicitly stated the direction of the paper, and as will be seen below, included all but one of the issues referred to by Collins, it does seem that the debate is about choice of emphasis. The following represent some more specific comments on the individual sections of the Comment.