Polling aggregator

A poll aggregator is a web site that predicts upcoming U.S. federal elections by gathering and averaging pre-election polls published by others. The site predicts the winner of a presidential election and post-election composition of the Senate and House of Representatives, as well as showing who is currently ahead where and by how much. It is useful in U.S. presidential elections because the presidency is determined by the winner of state by state elections (see Electoral College), and not by simple popular vote of the entire nation. Editorial commentary by the site's owners and others complements the data. Interest and web traffic peak during the last few weeks before the election.

How individual polls are averaged varies from site to site. Some aggregators weight polls in the average based on past pollster accuracy, age of the poll, or other more subjective factors. The averaging method has been criticized by at least one statistician because it doesn't weight them by sample size. In this way the resulting average support percentages do not reflect the actual support percentage for any candidate of the pooled polls.

Veteran political journalist Bill Moyers has commented that poll aggregators are a good tool for sorting out the polls.

Real Clear Politics was the first such web site. It began aggregating polls in 2002 for the congressional elections that year. Several sites existed by 2004, including Andrew S. Tanenbaum's Electoral-vote.com, and Sam Wang's Princeton Election Consortium. Relative newcomer FiveThirtyEight began in 2008 by baseball statistician Nate Silver and has been lauded for the quality of its analysis. Pollster.com by Mark Blumenthal, now affiliated with the Huffington Post as Huffpost Pollster, has likewise been given a top ranking for the depth and breadth of its chartable polling data. Since 2010 the political blog Talking Points Memo has also sponsored a "PollTracker" feature which aggregates opinion polls. Other noteworthy examples include Drew Linzer's Votamatic, Josh Putnam's Frontloading HQ as well as Election Projection by Scott Elliott and Politics by the Numbers by Jay DeSart and Tom Holbrook. For an aggregator of poll aggregators see the PollyVote, which combines different polling averages as one component of a combined forecast of the US presidential election result.

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