The OECD Trade and Environment Working Paper series is designed to make available to a wide readership selected studies by OECD staff or outside consultants. OECD Working Papers should not be reported as representing the official views of the OECD or of its member countries. The opinions expressed and arguments employed are those of the authors. Working Papers describe preliminary results or research in progress by the author(s) and are published to stimulate discussion on a broad range of issues on which the OECD works. Comments on Working Papers are welcomed, and may be sent to the Environment Directorate or the Trade and Agriculture Directorate, OECD,