NOTICE: The project that is the subject of this report was approved by the Council of the National Academy of Sciences. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance.

This study was supported by Contract No. DE-AM01-99PO80016, Task Order DE-AT01-00NN40153, A000 between the National Academy of Sciences and the Department of Energy and the John D. and Catherine T. MacArthur Foundation. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

Additional copies of this report are available from the Committee on International Security and Arms Control, 2101 Constitution Avenue, N.W., Washington, D.C. 20418, (202) 334-2811, cisac@nas.edu ; the report is also available online at http://www.nap.edu .