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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This study was supported by the Department of Commerce/U.S. Bureau of Census, Award No. YA1323-04-AE-0084, Department of Health and Human Services/ Centers for Disease Control and Prevention, Contract No. 200-2005-M-13677, Department of State, Award Nos. S-LMAQM-05-GR-097 and S-AQMPD-05-C-1176, National Aeronautics and Space Administration, Award No. W24749, U.S. Agency for International Development, Award No. DOT-S-00-04-00039-00. Any opinions, findings, and conclusions or recommendations contained in this publication are those of the authors and do not necessarily reflect the views of the organizations or agencies that provided support for the project. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Government.

International Standard Book Number-13: 978-0-309-10354-1 (Book)

International Standard Book Number-10: 0-309-10354-1 (Book)

International Standard Book Number-13: 978-0-309-66672-5 (PDF)

International Standard Book Number-10: 0-309-66672-4 (PDF)

Library of Congress Control Number 200792664

Cover: Design by Michael Dudzik. Photo credits: IKONOS satellite image off the island of Java, Indonesia, courtesy of GeoEye; hand-held computer courtesy of U.S. Census Bureau, Public Information Office (; Ecuador street scene courtesy of Clara Natoli (Rome, Italy) (

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