Download this Paper Open PDF in Browser

Combining Forecasts: An Application to Elections

27 Pages Posted: 1 Aug 2011 Last revised: 30 Aug 2014

Andreas Graefe

Ludwig Maximilians University of Munich - Department of Communication Science and Media Research

J. Scott Armstrong

University of Pennsylvania - Marketing Department

Randall J. Jones

University of Central Oklahoma

Alfred G. Cuzan

University of West Florida

Date Written: January 28, 2013

Abstract

We summarize the literature on the effectiveness of combining forecasts by assessing the conditions under which combining is most valuable. Using data on the six U.S. Presidential elections from 1992 through 2012, we then report the reduction in error obtained by averaging forecasts within and across four election forecasting methods: poll projections, expert judgment, quantitative models, and the Iowa Electronic Markets. Across the six elections, the resulting combined forecasts were on average more accurate than each of the component methods. The gains in accuracy from combining increased with the number of forecasts used, especially when these forecasts were based on different methods and different data, and in situations involving high uncertainty. Combining yielded error reductions ranging from 16% to 59%, compared to the average errors of the individual forecasts. This improvement is substantially greater than the 12% reduction in error that had been previously reported for combining forecasts.

Keywords: election forecasting, combining, prediction markets, polls, econometric models, expert judgment

JEL Classification: C53, E17, C40

Suggested Citation

Graefe, Andreas and Armstrong, J. Scott and Jones, Randall J. and Cuzan, Alfred G., Combining Forecasts: An Application to Elections (January 28, 2013). International Journal of Forecasting, 30(1), 43-54; Revised and extended version of a paper presented at the American Political Science Association (APSA) 2011 Annual Meeting. Available at SSRN: https://ssrn.com/abstract=1902850

Andreas Graefe (Contact Author)

Ludwig Maximilians University of Munich - Department of Communication Science and Media Research ( email )

Geschwister-Scholl-Platz 1
Munich, Bavaria 80539
Germany

HOME PAGE: http://www.andreas-graefe.org

J. Scott Armstrong

University of Pennsylvania - Marketing Department ( email )

700 Jon M. Huntsman Hall
3730 Walnut Street
Philadelphia, PA 19104-6340
United States
215-898-5087 (Phone)
215-898-2534 (Fax)

HOME PAGE: http://marketing.wharton.upenn.edu/people/faculty/armstrong.cfm

Randall J. Jones

University of Central Oklahoma ( email )

100 North University Drive
Edmond, OK 73034
United States

Alfred G. Cuzan

University of West Florida ( email )

11000 University Parkway
Pensacola, FL 32514-5750
United States

Paper statistics

Downloads
472
Rank
48,928
Abstract Views
2,691