Editing Proportional representation (section)

===Gerrymandering===
First-past-the-post elections are dependent on the drawing of boundaries of their [[single-member district]]s, a process vulnerable to political interference ([[gerrymandering]]) even if districts are drawn in such a way as to ensure approximately equal representation. However, because voter turnout varies from district to district and because in one district a winner might take 80 percent of the vote while in another the winner might be elected with only 30 percent of the vote, there might be wide variation in votes-per-winner, even if districts are drawn in such a way as to take in equivalent population. As one party might take its seats with a low votes-per-winner ratio while another party might not have that advantage, the result is likely to be disproportionate.<ref>{{Cite web|url=https://blogs.lse.ac.uk/politicsandpolicy/voters-dislike-disproportionality-in-electoral-systems/|title=Voters dislike disproportionality in electoral systems – even when it benefits the party they support|date=29 January 2020}}</ref>

To compound the problem, boundaries have to be periodically re-drawn to accommodate population changes. Even apolitically drawn boundaries can unintentionally produce the effect of gerrymandering, reflecting naturally occurring concentrations.<ref name="amyRCNV">{{cite book |last=Amy |first=Douglas J |title=Real Choices / New Voices, How Proportional Representation Elections Could Revitalize American Democracy |publisher=[[Columbia University Press]] |date=2002 |isbn=9780231125499}}</ref>{{rp|65}}

PR systems, due to having larger districts with multiple members, are less prone to gerrymandering{{snd}}research suggests five-seat districts or larger are immune to gerrymandering.<ref name="amyRCNV" />{{rp|66}}

Equality of size of multiple-member districts is not important (the number of seats can vary) so districts can be aligned with historical territories of varying sizes such as cities, counties, states or provinces. Later population changes can be accommodated by simply adjusting the number of representatives in the district, without having to re-draw a single boundary. For example, Mollison in his 2010 plan for STV for the UK divided the country into 143 districts and then allocated varying number of seats to each district (to add up to the existing total of 650 MPs) depending on the number of voters in each but with wide ranges (his five-seat districts include one with 327,000 voters and another with 382,000 voters). His district boundaries follow historical [[county]] and [[local authority]] boundaries, yet he achieves more uniform representation than does the [[Boundary Commissions (United Kingdom)|Boundary Commission]], the body responsible for balancing the UK's [[First-past-the-post voting|first-past-the-post]] constituency sizes.<ref name="DMstvPdf" /><ref name="DMstvSite">{{cite web |last1=Mollison |first1=Denis |title=Fair votes in practice: STV for Westminster |url=http://www.macs.hw.ac.uk/~denis/stv4uk/ |publisher=[[Heriot-Watt University]] |access-date=3 June 2014 |date=2010}}</ref>

Mixed-member systems are susceptible to gerrymandering for the local seats that remain a part of such systems. Under [[parallel voting]], a [[semi-proportional representation|semi-proportional system]], there is no compensation for the effects that such gerrymandering might have. Under MMP, the use of compensatory list seats makes gerrymandering less of an issue. However, its effectiveness in this regard depends upon the features of the system, including the size of the regional districts, the relative share of list seats in the total, and opportunities for [[Mixed-member proportional representation#Collusion|collusion]] that might exist. A striking example of how the compensatory mechanism can be undermined can be seen in the [[2014 Hungarian parliamentary election]], where the leading party, [[Fidesz]], combined gerrymandering and decoy lists, which resulted in a two-thirds parliamentary majority from a 45% vote.<ref>{{cite web |last1=Scheppele |first1=Kim Lane |title=Legal But Not Fair (Hungary) |url=https://krugman.blogs.nytimes.com/2014/04/13/legal-but-not-fair-hungary/ |website=The Conscience of a Liberal, Paul Krugman Blog |publisher=[[The New York Times Co.]] |access-date=12 July 2014 |date=13 April 2014}}</ref><ref>{{cite web |author1=Office for Democratic Institutions and Human Rights |author-link1=Office for Democratic Institutions and Human Rights |title=Hungary, Parliamentary Elections, 6 April 2014: Final Report |url=http://www.osce.org/odihr/elections/hungary/121098 |website=[[OSCE]] |date=11 July 2014}}</ref> This illustrates how certain implementations of [[Mixed electoral system|mixed systems]] (if non-compensatory or insufficiently compensatory) can produce moderately proportional outcomes, similar to parallel voting.{{Citation needed|date=May 2025}}