Talk:Australian electoral system: Difference between revisions
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m (Why two-party domination? Added multiple reasons) |
m (T&G refers to center squeeze when explaining Duverger's law - adding that and pdf) |
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::: That would be IRV. STV, being a proportional representation method, doesn't seem to cause two-party domination unless limited by something else. In Australia's case, it seems that IRV's pull is greater than STV's push (as it were). As far as I know, neither academic research nor EM gives any definite answer to why two-party domination occurs with IRV, and whether it can be generalized to all majoritarian single-winner methods. Possible reasons for two-party domination are: |
::: That would be IRV. STV, being a proportional representation method, doesn't seem to cause two-party domination unless limited by something else. In Australia's case, it seems that IRV's pull is greater than STV's push (as it were). As far as I know, neither academic research nor EM gives any definite answer to why two-party domination occurs with IRV, and whether it can be generalized to all majoritarian single-winner methods. Possible reasons for two-party domination are: |
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:::: * Center squeeze (unstable IRV outcomes when there are three strong contenders, e.g. Burlington). Condorcet doesn't have that. |
:::: * Center squeeze (unstable IRV outcomes when there are three strong contenders, e.g. Burlington; see also Taagepera and Grofman p. 346). Condorcet doesn't have that. |
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:::: * Favorite betrayal (IRV has this, Condorcet does too, usual cardinal methods don't) |
:::: * Favorite betrayal (IRV has this, Condorcet does too, usual cardinal methods don't) |
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:::: * District magnitude (SNTV with s seats seems to produce s+1-party rule in Japan, https://www.jstor.org/stable/193914, but on the other hand, France with single-member district [[top-two runoff]] has four or so party rule) |
:::: * District magnitude (SNTV with s seats seems to produce s+1-party rule in Japan, https://www.jstor.org/stable/193914, but on the other hand, France with single-member district [[top-two runoff]] has four or so party rule) |
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:::: * Natural packing/cracking effects (a party that has 10% support everywhere being given only a few seats because it's the outright favorite few places, e.g. the Liberal Democrats in the UK). This affects all single-member district methods unless they have top-up seats. |
:::: * Natural packing/cracking effects (a party that has 10% support everywhere being given only a few seats because it's the outright favorite few places, e.g. the Liberal Democrats in the UK). This affects all single-member district methods unless they have top-up seats. |
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:::: * Too few dimensions to issue space (analogous to Malta, and Taagepera and Grofman's https://doi.org/10.1111/j.1475-6765.1985.tb00130.x) |
:::: * Too few dimensions to issue space (analogous to Malta, and Taagepera and Grofman's https://doi.org/10.1111/j.1475-6765.1985.tb00130.x pdf: https://www.socsci.uci.edu/~bgrofman/42%20Grofman.%20Rethinking%20Duverger%27s%20Law..pdf) |
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:::: * Some interplay of these effects (e.g. low dimensionality issue space kept low by center squeeze effects) |
:::: * Some interplay of these effects (e.g. low dimensionality issue space kept low by center squeeze effects) |
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::: The only things that seem definite are: IRV can tether STV's otherwise multiparty rule, and single-member districts don't force two-party rule (counterexamples being runoff voting in France, approval in Greece). Even Plurality's two-party rule may sometimes be limited to a local scope (Canada, India). [[User:Kristomun|Kristomun]] ([[User talk:Kristomun|talk]]) 17:41, 3 July 2022 (UTC) |
::: The only things that seem definite are: IRV can tether STV's otherwise multiparty rule, and single-member districts don't force two-party rule (counterexamples being runoff voting in France, approval in Greece). Even Plurality's two-party rule may sometimes be limited to a local scope (Canada, India). [[User:Kristomun|Kristomun]] ([[User talk:Kristomun|talk]]) 17:41, 3 July 2022 (UTC) |
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