One way to looks at common election methods is this:
Winner-take-all
Non-Proportional
FPTP Instant-runoff voting
Single-member plurality also known as ranked voting, preferential voting
. elects just one member in the district
18 -82 percent of votes effective 50 (sometimes 49)-82 percent of votes effective
Proportional Representation
Single Transferable Voting List PR Mixed Member Proportional
STV MMP
elects multiple members elects multiple members elects multiple members
in the district in the district or at-large through pooling votes
elects single member
in each district.
80-90 percent of votes effective
(Denmark elects multiple members in the district, and also elects multiple members through overall pooling of the vote)
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looking at election ,methods
What is First past the post? What is STV? What is list PR ? MMP?
Plurality single-winner is FPTP
It is also known as Single-member Plurality (SMP).
Block Voting (sometimes called plurality block voting) = plurality multi-winner
each voter can vote for more than one candidate
plural voting where plurality is used to determine the winners = block voting.
in each system above, each voter has as many votes as the seats to fill, sort of a general rule for systems that are not-proportional
either, there is only one winner or only one group can take all the seats in the district
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STV is multi-winner but each voter has single vote (many preferences but a single vote)
Semi-proportional systems
SNTV is multi-winner but each voter has single vote and marks only one preference
Cumulative Voting is like block voting but a voter can lump votes on just one candidate
so it is multiple voting but voter can vote just for one candidate with no loss of votes to cast.
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say two, three (or four) layers of analysis of elections
Election contests are really just votes and districts or contests. And sometimes a bit more.
So there's votes (A) and sometimes what comes after (B)
and
district winners (C) and sometimes what comes after (D)
Different systems use different steps:
FPTP has A and C
STV (and IRV) has A, B and C
MMP is done in four steps -- district seats - A, C, and overall seats - A, D, where D is done with reference to district seat winners (compensatory method)
Danish-style MMP is done in four steps
-- district seats - A, C, where C is based on party proportions of votes cast in each district
-- overall seats - A, D, where D is done with reference to district seat winners.
Fair Vote Canada's Rural-Urban PR (with rural top-up)
seats are allocated separately urban versus rural
urban (STV) - in each urban district A, B, C
rural (MMP) - each rural district A, C, then rural overall - A, D, where D is done with reference to rural district seat winners.
(not clear to me if rural votes would cast vote in district and a vote for party, or just one vote that would be used for both district contest and to set overall party shares of the seats but that decision would be made by those who set up the system
- RUPR is not currently used anywhere so no existing system can be used as example)
Five stages of elections
the vote and vote transfers
A. vote X voting or the First Preference in preferential voting system
B. vote transfers (only where preferential votes are used - STV or Instant-Runoff Voting)
(some votes are transferred before they are finally used to elect someone.
the voter's ranked prefernce control the vote transfers.
the district seats and other seats (top-up) if any
C. district seats allocated according to vote tallies, as per votes as used -
the final in preferential voting or the first and only vote cast in X voting
(list PR applies votes cast to set party shares of the seats)
D. in MMP systems, top-up seats are allocated after district contest winners declared. (see below)
FPTP, Alternative Voting and STV has no D level
E Giving us the final seat balance in the chamber
affix label: either majority government or minority government,
depending on if the party with the most seats has majority of seats in the legislature. (whether or not any party has taken a majority of the seats)
if it is minority, coalition or some other means of getting majority of members to support government, or maybe there is no structured relationship
and either government falls or it lives on to the usual term.
Whether government is a majority government or a minority government and how long it lasts is not up to votes cast, at least not directly.
it is just up to seats won,
and in Canada currently, under FPTP, those seats are filled in 338 separate little sub-battles with votes being used in the district where it is cast or not at all - often not at all.
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The five stage of elections under MMP
MMP elects district winners and adds seats (top-up seats at the party level)
the system used in New Zealand
district winners are arrived at through A and C in each district
Overall top-up
to set the top-up
the vote used is the party vote, separate from the district vote and cast just for party of choice is compared to the district seats won.
level A. vote X voting
votes for each party are calculated
the percentages of votes is transposed to number of seats that are the party's due.
level D.
In MMP systems, top-up seats are allocated after district contest winners declared
(party vote shares are arrived at,
parties whose votes are effective are declared (not all parties are represented) and the seats that each of them is due is calculated,
top-up is difference between district seats already won and what each party with representation is due.
(The represented party seat shares may be calculated prior to determination of district winners (C).
Level C does have an effect if winning a district seat means a party will get its due share of seats, and the party would not otherwise (a way around electoral threshold) or
if a party wins more district seats than it is due, some systems allocate additional top-up seats to give small compensation to the other parties for the overhang, so those additional seats change the number of seats in the chamber.
generally the number of district seats won (C) has no effect on the fair final seat balance in the chamber as determined to set the top-up.
(And that is why it is claimed that people in an MMP system can look at party votes cast and predict what the new government will look like even if they don't know how many district seats a party has won.
but note in New Zealand, the party share of seats is determined based on party vote, not the district vote, so there can be variance in party vote shares versus district seat shares just due to that ( not to menton the inefficiency of FPTP)
Above produces E the final seat balance in the chamber. Under MMP, the seat balance in the chamber reflects party votes cast,
specifically votes that were cast for the parties that were due representation, as much as possible
-- some parties may have more representation than their due, because they won more district seats than their due.
In many MMP systems, a party will get all its district seats even if they are beyond the seat equivalent of the party's share of votes.
But in Germany as of recently, seat shares of rep. parties will be more in line with vote shares of rep. parties as overhang is not possible.
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