ACKNOWLEDGMENTS We gratefully acknowledge Edward Balkovich (RAND) and Jonathan Koomey (Lawrence Berkeley National Laboratory) for formal reviews that substantially improved this report. The report further benefited from review comments by Robert Anderson (RAND), Charles Grantham (The Institute for the Study of Distributed Work at the University of California at Berkeley), Imre Gyuk (U.S. Department of Energy), Kurt Roth (TIAX LLC), and several anonymous reviewers of earlier drafts. Many other individuals in government, industry, and the research community generously shared their data, knowledge, insights, and opinions with us during the course of this study. We thank all of them. Finally, we thank David Adamson, Debra Knopman, Janet DeLand, and Jeri O’Donnell for their assistance in the final preparation of this report. xxiii