A swing is particularly useful for analysing change in voter support over time, or as a tool for predicting the outcome of elections in constituency-based systems.
An assumption underlies extrapolated national calculations: that all districts will experience the same swing as shown in a poll or in a place's results.
[5][6] In Australia, the term "swing" refers to the change in the performance of a political party or candidate in an election or opinion poll.
[8] In multiparty systems exit polls frequently include a question as to voting behavior in the last applicable election.
Based on those exit polls "voter migration" (where vote gains for a specific party came from and losses of another went to) analyses are published and discussed in election coverage.