… I’ve spent much of the past few weeks updating our polling database in preparation for the launch of our 2014 Senate forecasts. In conjunction with those forecasts, we’ll also release our first full set of pollster ratings since 2010. But for now, my aim will be to consider the results for the polls as a whole: how accurate the average poll is in different types of races — presidential elections, gubernatorial elections and so forth — and how this has changed over time.
I’ll conduct this analysis in the context of the seeming contradiction we identified: The polls have managed to produce high-quality output (pretty good forecasts of election outcomes) with worse and worse input (fewer and fewer people responding to them). It’s something of a paradox. CONT.
Nate Silver, FiveThirtyEight