The Journal of The Journal of Economic Perspectives Economic Perspectives The Journal of Spring 2017, Volume 31, Number 2 Economic Perspectives Symposia Recent Ideas in Econometrics Susan Athey and Guido W. Imbens, “The State of Applied Econometrics: Causality and Policy Evaluation” Hamish Low and Costas Meghir, “The Use of Structural Models in Econometrics” James H. Stock and Mark W. Watson, “Twenty Years of Time Series Econometrics in Ten Pictures” Sendhil Mullainathan and Jann Spiess, “Machine Learning: An Applied Econometric Approach” James L. Powell, “Identication and Asymptotic Approximations: A journal of the Three Examples of Progress in Econometric Theory” American Economic Association Joshua D. Angrist and Jörn-Steffen Pischke, “Undergraduate Econometrics Instruction: Through Our Classes, Darkly” Spring 2017 Volume 31, Number 2 Spring 2017 Volume Are Measures of Economic Growth Biased? Martin Feldstein, “Underestimating the Real Growth of GDP, Personal Income, and Productivity” Chad Syverson, “Challenges to Mismeasurement Explanations for the US Productivity Slowdown” Erica L. Groshen, Brian C. Moyer, Ana M. Aizcorbe, Ralph Bradley, and David Friedman, “How Government Statistics Adjust for Potential Biases from Quality Change and New Goods in an Age of Digital Technologies: A View from the Trenches” Articles Hunt Allcott and Matthew Gentzkow, “Social Media and Fake News in the 2016 Election” Susan Athey and Andrzej Skrzypacz, “Yuliy Sannikov: Winner of the 2016 Clark Medal” Recommendations for Further Reading Spring 2017 The American Economic Association The Journal of Correspondence relating to advertising, busi- Founded in 1885 ness matters, permission to quote, or change Economic Perspectives of address should be sent to the AEA business EXECUTIVE COMMITTEE office: [email protected]. 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The JEP TERRY CALVANI, Freshfields Bruckhaus Deringer LLP is published quarterly (February, May, August, November) by the American Economic Association, 2014 Washington, DC Broadway, Suite 305, Nashville, TN 37203-2418. Annual dues for regular membership are $20.00, $30.00, or $40.00 depending on income; for an additional $15.00, you can receive this journal in print. E-reader ADMINISTRATORS versions are free. For details and further information on the AEA go to https://www.aeaweb.org/. Director of Finance and Administration Periodicals postage paid at Nashville, TN, and at additional mailing offices. BARBARA H. FISER POSTMASTER: Send address changes to the Journal of Economic Perspectives, 2014 Broadway, Suite 305, Convention Manager Nashville, TN 37203. Printed in the U.S.A. GWYN LOFTIS The Journal of Economic Perspectives Contents Volume 31 • Number 2 • Spring 2017 Symposia Recent Ideas in Econometrics Susan Athey and Guido W. Imbens, “The State of Applied Econometrics: Causality and Policy Evaluation” ................................3 Hamish Low and Costas Meghir, “The Use of Structural Models in Econometrics” ..............................................33 James H. Stock and Mark W. Watson, “Twenty Years of Time Series Econometrics in Ten Pictures” .............................................59 Sendhil Mullainathan and Jann Spiess, “Machine Learning: An Applied Econometric Approach”. .87 James L. Powell, “Identification and Asymptotic Approximations: Three Examples of Progress in Econometric Theory” .................. 107 Joshua D. Angrist and Jörn-Steffen Pischke, “Undergraduate Econometrics Instruction: Through Our Classes, Darkly” ..................... 125 Are Measures of Economic Growth Biased? Martin Feldstein, “Underestimating the Real Growth of GDP, Personal Income, and Productivity” ........................................... 145 Chad Syverson, “Challenges to Mismeasurement Explanations for the US Productivity Slowdown” ...................................... 165 Erica L. Groshen, Brian C. Moyer, Ana M. Aizcorbe, Ralph Bradley, and David M. Friedman, “How Government Statistics Adjust for Potential Biases from Quality Change and New Goods in an Age of Digital Technologies: A View from the Trenches” ....................... 187 Articles Hunt Allcott and Matthew Gentzkow, “Social Media and Fake News in the 2016 Election” ............................................. 211 Susan Athey and Andrzej Skrzypacz, “Yuliy Sannikov: Winner of the 2016 Clark Medal” .............................................. 237 Features Timothy Taylor, “Recommendations for Further Reading” ................... 257 Statement of Purpose The Journal of Economic Perspectives attempts to fill a gap between the general interest press and most other academic economics journals. The journal aims to publish articles that will serve several goals: to synthesize and integrate lessons learned from active lines of economic research; to provide economic analysis of public policy issues; to encourage cross-fertilization of ideas among the fields of economics; to offer readers an accessible source for state-of-the-art economic thinking; to suggest directions for future research; to provide