An election exit poll is a poll of voters taken immediately after they have exited the polling stations. A similar poll conducted before actual voters have voted is called an entrance poll. Pollsters – usually private companies working for newspapers or broadcasters – conduct exit polls to gain an early indication as to how an election has turned out, as in many elections the actual result may take hours or even months to count.
There are different views on who invented the exit poll. Marcel van Dam, Dutch sociologist and former politician, claims to be the inventor, by being the first to implement one during the Dutch legislative elections on February 15, 1967. Other sources say Warren Mitofsky, an American pollster, was the first. For CBS News, he devised an exit poll in the Kentucky gubernatorial election in November that same year. Not withstanding this, the mention of the first exit polls date back to the 1940s when such a poll was held in Denver, Colorado.
Exit polls are also used to collect demographic data about voters and to find out why they voted as they did. Since actual votes are cast anonymously, polling is the only way of collecting this information. Exit polls have historically and throughout the world been used as a check against, and rough indicator of, the degree of election fraud. Some examples of this include the 2004 Venezuelan recall referendum, and the 2004 Ukrainian presidential election.
They are used to command a mandate as well as to determine whether or not a particular political campaign was successful or not.
The distribution of votes is not even across different polling stations, and also varies at different times of day. As a result, a single exit poll may give an imperfect picture of the national vote. Instead, the exit poll is primarily used to calculate swing and turnout. Pollsters return to the same polling stations at the same times at each election, and by comparing the results with previous exit polls they can calculate how the distribution of votes has changed in that constituency. This swing is then applied to other similar constituencies, allowing an estimate of how national voting patterns have changed. The polling locations are chosen to cover the entire gamut of society and where possible, to include especially critical marginal seats. Data is presented in one of three ways, either as a table, graph or written interpretation.