Lies, Damn Lies, and Pre-Election Polling
1. Ten (10) web appendix tables. 2. Eleven (11) web appendix figures. 3. Five page discussion of intentions problem. December 31, 2008Lies, Damn Lies, and Pre-Election Polling By Elias Walsh, Sarah Dolfin and John DiNardo ∗ In this paper we ask the question: how well do pre–election polls forecast the actual results of elections in the U.S.? The question is interesting for a number of reasons. First, even polling data suggests about 1/3 of polling respondents do not believe that polls work in “the best interests of the general public ” 1 The situation is such that even many national governments have undertaken to restrict some aspect of pre–election polling. A 1997 international survey of governments, for example, found 30 of 78 surveyed nations had some kind of ban on publication of poll results (Røhme, 1992). Second, there is a a strong presumption in the literature on professional forecasting in other contexts which do not rely on sampling per se, (such as interest rate forecasting) that forecasts will be biased. 2 There are a variety of explanations for why forecasts will be biased; one “honest ” motivation is that pollsters may avoid reporting results from the unavoidable “atypical ” polls. Third, in the literature in economics it is sometimes assumed that polls are unbiased forecasts (of potentially time– varying) underlying preferences for candidates. For a recent example, see Keppo et al. (2008) who characterize pre–election polling as a “noisy observation of the actual election outcome that