Modeling Election Forecasts the FiveThirtyEight Way
Years ago Nate Silver of FiveThirtyEight.com, a blog seeking to educate the public about elections forecasting, established his model as one of the most accurate in existence, rising from a fairly unknown statistician working in baseball to one of the most respected names in election forecasting. In this article he describes all the factors that go into his predictions. A fascinating overview of the process of modeling a chaotic system.
FJP: It is fascinating.
With national, regional and statewide polling feeding off oftentimes conflicting information, and then still other polling that has what Silver calls “house effects" (meaning that a poll is an outlier, skewing Democratic or Republican in relation to other polls), all within what will be a tight, tight, tight race, Silver lays out both the art and science of his models.
For example, take Silver’s analysis of Florida:
Right now, the polls there show almost an exact tie. But the model views Florida as leaning toward Mr. Romney, for several reasons.
First, the polls showing a tie there were mostly conducted among registered voters rather than likely voters. Republicans typically improve their standing by a point or two when polling firms switch from registered voter to likely voter polls, probably because Republican voters are older, wealthier, and otherwise have demographic characteristics that make them more reliable bets to turn out. The model anticipates this pattern and adjusts for it, bolstering Mr. Romney’s standing by a point or two whenever it evaluates a registered-voter poll.
In addition, the fundamentals somewhat favor Mr. Romney in Florida. The state has been somewhat Republican-leaning in the past, and its economy is quite poor. Mr. Romney has raised more money than Mr. Obama there, and its demographics are not especially strong for Mr. Obama. The model considers these factors in addition to the polls in each state. In the case of Florida, they equate to Mr. Romney having about a 60 or 65 percent chance of winning it, and Mr. Obama probably has easier paths to 270 electoral votes.
If you’re a political junky whose heart skips a beat with the daily polls, read through. As said before, it’s a fascinating look at how political forecasting is done by one of the best in the business.
Image: While US presidential politics — and its electoral college — is a winner take all system that leads to strict Red State versus Blue State divisions across the country, this map of the 2008 presidential elections provided by the University of Michigan’s Mark Newman shows that if you look at the country at a county by county level, the country’s political leanings are decidedly purple. Meaning that slight ebbs can turn an entire state red (Republican) or blue (Democratic).