Editing Additional-member system (section)

=== AMS vs. MMP ===
AMS is used by some as another term to mean the broadly same type of system called [[mixed-member proportional representation]] (MMP) in New Zealand.{{Citation needed|date=September 2024}} As the term additional member system is used here, AMS is unlike some MMP systems more true to its name, because it does not compensate for the disproportionate results caused by a party taking so many district seats that the fixed number of top-up seats cannot compensate. Such is the case where the leading party takes [[overhang seat]]s and the legislature has a fixed number of seats. In 'true' MMP systems, [[leveling seats]] (extra additional members) are filled in such a way as to ensure parties have proportional representation, but not in the AMS as used in the UK.

Due to the problem of district contests electing too many members for leading parties (overhang), the AMS systems discussed here, instead of producing fully proportional results, often produce only [[semi-proportional representation]]. However, even semi-proportional representation is a considered by some a great advance on an electoral system that uses only the [[First past the post|first-past-the-post]] voting system, where the number of seats a party takes only vaguely reflects the number of votes that party receives.<ref name=":0">{{Cite web |title=Electoral systems |url=https://consoc.org.uk/the-constitution-explained/electoral-systems/#additional-member-system |access-date=2024-09-04 |website=The Constitution Society |language=en-GB}}</ref>

The term ''additional member system'', as introduced by the [[Hansard Society]], has been confused in the literature with the term ''mixed member proportional'' ''representation'' (in the broader sense) coined by [[New Zealand]]'s [[Royal Commission on the Electoral System]] (1984–1986).<ref name="LundbergElecSysRev">{{cite journal |last1=Lundberg |first1=Thomas Carl |year=2007 |title=Electoral System Reviews in New Zealand, Britain and Canada: A Critical Comparison |url=https://core.ac.uk/download/pdf/1395088.pdf |journal=[[Government and Opposition]] |volume=42 |issue=4 |pages=471–490 |doi=10.1111/j.1477-7053.2007.00232.x |s2cid=153862834}}</ref> The term AMS has been conflated also with [[parallel voting]], which is not a compensatory system and in New Zealand was offered under the name ''supplementary member system''. AMS has also been used to mean any system with additional members (both parallel voting and compensatory systems), therefore any two-tiered mixed system with first-past-the-post and additional list members.<ref>{{Cite web |date=2020-11-28 |title=Mixed-member proportional |url=https://electowiki.org/wiki/Mixed-member_proportional |access-date=2024-09-09 |website=electowiki |language=en}}</ref> This is also why some unconventional systems, such as [[scorporo]] have also occasionally been described as 'additional member systems', although with compensatory systems this was also reinforced by the conflation of compensatory mixed systems and mixed-member proportional representation in general.