In computing, a aggregator, also termed a feed aggregator, feed reader, news reader, RSS reader or simply an aggregator, is client software or a web application that aggregates syndicated web content such as online newspapers, blogs, podcasts, and video blogs in one location for easy viewing.
A poll aggregator may also forecast the likely outcome of upcoming elections by gathering and analysing pre-election polls published by others, and/or utilizing other available politics-related information which, according to its methodology, may affect the outcome of an election. For example, an aggregator may attempt to predict the winner of a presidential election or the composition of a legislature, or it may focus on attempting to determine current opinion by smoothing out poll-to-poll variation. 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 aggregated varies from site to site. Some aggregators take a long- or short-term running/rolling average or average the polls at certain points in time, while other aggregators might take a weighted poll average (e.g., giving less weight to older polls), or use some other proprietary method of aggregation, based on such factors as 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. According to the American Association for Public Opinion Research, “[o]ther aggregators use regression-based analyses — a method for adjusting data to account for unusual results (“outliers”). Other aggregators combine additional data like historical election results or economic data with current polling data through statistical methods – these are often called modelers.”
Aggregators are not capable of accounting for systematic errors in the polls themselves. For instance, if pollsters are misjudging the turnout demographics, aggregators cannot undo these errors. Likewise, when there is a tendency to herd (i.e. for different pollsters to converge on a particular result to avoid being an outlier), aggregators will reflect this.
Aggregators are 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. Consequently to predict a winner, polls of individual states becomes more significant. An equivalent issue may arise in parliamentary systems if the legislature is sufficiently malapportioned as in Canada.