Forecasting Elections: Voter Intentions versus Expectations* David Rothschild Justin Wolfers Microsoft Research Dept of Economics and Ford School of Public Policy, and Applied Statistics Center, Columbia University of Michigan Brookings, CEPR, CESifo, IZA and NBER
[email protected] [email protected] www.ResearchDMR.com www.nber.org/~jwolfers Abstract Most pollsters base their election projections off questions of voter intentions, which ask “If the election were held today, who would you vote for?” By contrast, we probe the value of questions probing voters’ expectations, which typically ask: “Regardless of who you plan to vote for, who do you think will win the upcoming election?” We demonstrate that polls of voter expectations consistently yield more accurate forecasts than polls of voter intentions. A small-scale structural model reveals that this is because we are polling from a broader information set, and voters respond as if they had polled twenty of their friends. This model also provides a rational interpretation for why respondents’ forecasts are correlated with their expectations. We also show that we can use expectations polls to extract accurate election forecasts even from extremely skewed samples. This draft: November 1, 2012 Keywords: Polling, information aggregation, belief heterogeneity JEL codes: C53, D03, D8 * The authors would like to thank Stephen Coate, Alex Gelber, Andrew Gelman, Sunshine Hillygus, Mat McCubbins, Marc Meredith and Frank Newport, for useful discussions, and seminar audiences at AAPOR, Berkeley, Brookings, CalTech, Columbia, Cornell, the Conference on Empirical Legal Studies, the Congressional Budget Office, the Council of Economic Advisers, Harvard, Johns Hopkins, Maryland, Michigan, MIT, the NBER Summer Institute, University of Pennsylvania’s political science department, Princeton, UCLA, UCSD, USC, and Wharton for comments.