Given the rapidly proliferating number of polls and models predicting the election, the interesting question to be answered after the election is which did the best job. Poll aggregator Sam Wang says that a good prediction should:
Be precise, allowing us to pinpoint a narrow range of outcomes.
Change relatively little in the long term, giving us time to plan in advance.
Give a true sense of the uncertainty – a sense of knowing what we don’t know.
He also looks at the different methods used in the current toolbox of political predictions:
This year, Presidential political predictions have come in multiple flavors:
Purely poll-based (Princeton Election Consortium, Electoral-Vote.com),
Econometric start-of-season models (political scientists),
Mixed (FiveThirtyEight, Votamatic),
Wisdom-of-crowds (InTrade), and
Expert-based evaluations (Charlie Cook, other pundits).
He then gives five criteria for evaluating which one is the best, with the different methods to be scored after the election when the results are known.