After almost two years of collecting and combining forecasts from five different component methods, Polly has finally finished her job for the 2012 election. Polly’s final forecast of the popular two-party vote shares predicts Obama to gain 51.0% (v. Romney 49.0%).
Over the past 22 months since January 1st of 2011, Polly has continuously predicted Obama to win the popular vote. As shown in the graph below, the highest value for Obama (54.1) was reached in May 2011 with the killing of Osama bin Laden. Shortly after, the PollyVote forecast decreased and reached its lowest value in November 2011, predicting Obama to win 50.4% of the popular vote. At that time, Polly could draw only on few component forecasts, as the expert panel was not yet in place and only few forecasts from statistical models were available. This explains the somewhat higher volatility of the early forecasts.
In 2012, with an increasing number of component forecasts available, Polly’s forecast moved in a much narrower range, with a maximum of 52.6% at the beginning of April and a minimum of 50.9% in late October. Thus, range of her forecast was only 1.7 percentage points.
One or more of Polly’s components will of course provide more accurate Election Eve forecasts than Polly, and it is easy to identify the most accurate forecast after the fact. However, at the time of making a prediction, it is difficult to pick the most accurate forecasts, in particular when making forecasts for long time horizons that involve much uncertainty.
The PollyVote is designed for situations that involve much uncertainty. This means that it is most useful months or years prior to the election, not for an Election Eve forecast, when it is usually sufficient to look at the latest poll average.
Polly has a perfect track record in predicting the popular vote winner, also for long time horizons. In 2004, starting eight months in advance, and in 2008 fourteen months ahead, Polly always predicted the correct winner. This time around Polly has continuously predicted Obama to win the two-party vote since her first forecast was released on January 1, 2011, almost two years before the election. With her final forecast of 51.0% for Obama, and all of her five components pointing to an Obama victory, Polly is confident that her perfect track record will remain.