- Gallagher Index
The Gallagher Index (or least squares index) is used to measure the disproportionality of an electoral outcome, that is the difference between the percentage of votes received and the percentage of seats a party gets in the resulting legislature. This is especially useful for comparing proportionality across
electoral systems. The index involves taking the square rootof half the sumof the squares of the difference between percent of vote and percent of seats (as whole numbers) for each of the political parties.
The index weighs the deviations by their own value, creating a responsive index, ranging from 0 to 100. The lower the index value the lower the disproportionality and vice versa. Michael Gallagher, who created the index, included 'other' parties as a whole category, and
Arend Lijphartmodified it, excluding those parties. Unlike the well-known Loosemore-Hanby index, the Gallagher index is less sensitive to small discrepancies.
Example of calculating disproportionality
This table uses the New Zealand 2005 election result. Note: New Zealand voters have two votes. This list uses the "party vote", which determines the proportionality of the House; the "electorate vote" determines the local member.
Thus the disproportionality of the 2005 New Zealand election is 1.11.
Sainte-Laguë Indexis considered by Gallagher to be "probably the soundest of all the measures". This is closely related to the Pearson's chi-square testwhich has better statistical underpinning.:
The Gallagher Index of the results of the
* Benoit, K. 2000. 'Which Electoral Formula Is the Most Proportional? A New Look with New Evidence.' "Political Analysis" 8:381-388.
* Gallagher, M. 1991. "Proportionality, Disproportionality and Electoral Systems." "Electoral Studies" 10:33-51.
* Gallagher, M. 1992. 'Comparing Proportional Representation Electoral Systems: Quotas, Thresholds, Paradoxes and Majorities.' "British Journal of Political Science" 22:469-496.
* Gallagher, M and Mitchell P. (eds). 2005. "The Politics of Electoral Systems" Oxford: Oxford University Press. Appendix B. ISBN 0-19-925756-6
* P Kestelman, [http://www.votingmatters.org.uk/ISSUE10/P6.HTM Quantifying Representativity] ", "Voting matters", Issue 10, March 1999.
Wikimedia Foundation. 2010.
Look at other dictionaries:
Gallagher — may refer to: Contents 1 People 2 Sport 3 Politics 4 … Wikipedia
Index of chess articles — Contents 1 Books 2 General articles 2.1 0–9 2.2 A … Wikipedia
Michael Gallagher (academic) — Michael Gallagher is a political scientist. He is Professor of Comparative Politics and head of the Department of Political Science at the University of Dublin, Trinity College. Contents 1 Education 2 Career 3 Works … Wikipedia
Michael Gallagher — Michael or Mike Gallagher may refer to: Michael Gallagher (academic), British political scientist at Trinity College, Dublin, inventor of the Gallagher Index Michael Gallagher (bishop) (1866–1937), American bishop Michael Gallagher (British… … Wikipedia
Fred Gallagher — Frederick Gallagher (born 1969) is an American illustrator who has become a full time web cartoonist. He is best known as the artist, co creator, and now full owner of Megatokyo . He also goes by the name of Piro, the main character of Megatokyo … Wikipedia
John Gallagher (golfer) — John Gallagher, Scottish Golf Union (born April 17, 1981) is a Scottish international amateur golfer. His most prolific victory came at the 2007 Scottish Amateur Championship which was played at Prestwick Golf Club in Ayrshire. The final match… … Wikipedia
Noel Gallagher's High Flying Birds (album) — Noel Gallagher s High Flying Birds Studio album by Noel Gallagher s High Flying Birds Released … Wikipedia
Noel Gallagher — Background information Birth name Noel Thomas David Gallagher Born 29 May 1 … Wikipedia
Liam Gallagher — Pour les articles homonymes, voir Gallagher. Liam Gallagher Surnom Liam Gallag … Wikipédia en Français
Diana G. Gallagher — is an American author who writes books for children and young adults based on television series. She has contributed to book series based on Buffy the Vampire Slayer, Sabrina the Teenage Witch and Charmed, among others. Born in 1946, in Paterson … Wikipedia