Hostname: page-component-78c5997874-s2hrs Total loading time: 0 Render date: 2024-11-13T02:04:21.627Z Has data issue: false hasContentIssue false
  • English
  • Français

Bayesian Combination of State Polls and Election Forecasts

Published online by Cambridge University Press:  04 January 2017

Kari Lock  and
Andrew Gelman
Kari Lock*
Affiliation:
Department of Statistics, Harvard University, 1 Oxford St., Cambridge, MA 02138
Andrew Gelman
Affiliation:
Department of Statistics and Department of Political Science, Columbia University 1016 Social Work Bldg, New York, NY 10027. e-mail: gelman@stat.columbia.edu
*
e-mail: lock@stat.harvard.edu (corresponding author)
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

A wide range of potentially useful data are available for election forecasting: the results of previous elections, a multitude of preelection polls, and predictors such as measures of national and statewide economic performance. How accurate are different forecasts? We estimate predictive uncertainty via analysis of data collected from past elections (actual outcomes, preelection polls, and model estimates). With these estimated uncertainties, we use Bayesian inference to integrate the various sources of data to form posterior distributions for the state and national two-party Democratic vote shares for the 2008 election. Our key idea is to separately forecast the national popular vote shares and the relative positions of the states. More generally, such an approach could be applied to study changes in public opinion and other phenomena with wide national swings and fairly stable spatial distributions relative to the national average.

Type
Research Article
Information
Political Analysis , Volume 18 , Issue 3 , Summer 2010 , pp. 337 - 348
Copyright
Copyright © The Author 2010. Published by Oxford University Press on behalf of the Society for Political Methodology 

Footnotes

Authors' note: We thank Aaron Strauss and three anonymous reviewers for helpful comments.

References

Annenberg Public Policy Center. 2008. www.annenbergpublicpolicycenter.org/AreaDetails.aspx?myId=1.Google Scholar
Bates, D. 2005. Fitting linear models in R using the lme4 package. R News 5: 27–30.Google Scholar
Campbell, J. 1992. Forecasting the presidential vote in the states. American Journal of Political Science 36: 386–407.CrossRefGoogle Scholar
Erikson, R., and Sigman, K. 2008. Guest pollster: The Survey USA 50 state poll and the electoral college. www.pollster.com/blogs/guest_pollster_the_surveyusa_5.php.Google Scholar
Gelman, A., and King, G. 1993. Why are American presidential election campaign polls so variable when votes are so predictable? British Journal of Political Science 23: 409–51.Google Scholar
Gelman, A., Park, D., Shor, B., and Bafumi, J. 2009. Red state, blue state, rich state, poor state: Why Americans vote the way they do. 2nd ed. Princeton, NJ: Princeton University Press.Google Scholar
Hibbs, D. 2008. Implications of the bread and peacemodel for the 2008 US presidential election. Public Choice 137: 1–10.CrossRefGoogle Scholar
Lax, J., and Phillips, J. 2009. Gay rights in the states: Public opinion and policy responsiveness. American Political Science Review 103: 367–86.Google Scholar
Rosenstone, S. 1983. Forecasting presidential elections. New Haven, CT: Yale University Press.Google Scholar
Silver, N. 2008. www.fivethirtyeight.com.Google Scholar
Strauss, A. 2007. Florida or Ohio? Forecasting presidential state outcomes using reverse random walks. In Princeton University Political Methodology Seminar. Princeton, NJ: Princeton University Press.Google Scholar
Survey Sampling International. 2008. www.surveysampling.com.Google Scholar
SurveyUSA. 2008. http://www.surveyusa.com.Google Scholar
Wang, S. 2008. Princeton Election Consortium FAQ. Princeton, NJ: Princeton Election Consortium. http://election.princeton.edu/faq.Google Scholar
Wlezien, C., and Erikson, R. 2007. The horse race: What polls reveal as the election campaign unfolds. International Journal of Public Opinion Research 19: 74.Google Scholar