STV put simply -- Droop and Hare compared

A bare-bones explanation of STV is multi-member district where each voter has one vote. Votes are placed on candidates. Quota is determined, and anyone attaining quota is elected. As well, if necessary, surplus votes of quota-winners are transferred according to next usable marked preference.

If necessary, least-popular candidate are eliminated and their votes transferred (or one might say, conduct the process of IRV -- repeatedly eliminate the candidate who has the fewest votes, if necessary.

That part of IRV is identical to tht part of STV.

Process continues until all seats are filled by quota winners or until field of candidates is thinned to number of remaining open seats.

Only other difference between IRV and STV is: STV is multi-winner which means surplus vote of winners need to be transferred, which happens only in relative small number of rounds of counting.

sure there are various ways to conduct transfers of surplus votes. just as there are various ways to construct open-list PR, which is often overlooked in "simple explanations" of list PR.

Bearing in mind the DM, STV is just as proportional as list PR, if you use votes as placed at end.

With each winner having identical vote tally, or close to it for those elected in last round, there is no way this could not be true.

Of course transfers can affect the parties' tallies of votes. That is part of why they are used. so using first-round votes to assess STV proportionality is not fair.

One might say "Voting for that candidate counts as a vote for your party, but also a vote for that candidate, in the determination of which candidates get the seats won by your party. The candidates are seated in the order of their vote-counts. Any unfilled seats are then assigned to the remaining candidates in the list, in their listed-order."

Droop is not biased in favor of large parties. it is just more in favor of them than Hare, which is tougher on them (because it allows surplus votes to rest with early winners when large parties want their votes shared out best to take more seats).

Droop is lowest figure that allows no more to get quota than the number of seats. Anything more than that is un-necessarily large and may (or may not) affect the parties' seat counts. Using quota that is smaller than Droop, such as Imperiali can work also but in rare cases more might achieve quota than there are seats .

Where DM is large, difference between Hare and Droop is less than one percent of votes.

in DM-10, Droop is 9 percent plus 1, Hare is 10 percent.

so not much impact on large parties' rep.

at 21 DM, as used in NSW Aus., the difference is even smaller-

Hare 5 percent

Droop 4.54 percent,

hardly going to make much difference when parties and candidates are thousands of votes apart.

(under any STV system most of the candidates in the lead in the first count go on to be elected, despite any transfers.)

Process continues until all seats are filled by quota winners or until field of candidates is thinned to number of remaining open seats.

Droop produces more transferable votes following the announcement of the first-count winners, and these transfer are conducted prior to any elimination of candidates, so in certain cases, the use of the Droop quota ensures party's full slates are available longer. Under Hare, fewer votes are considered surplus so transfers are done quicker and candidates are eliminated sooner, thus potentially eliminating a candidate who if surviving, might have been elected as votes were transferred.

This is noted in Lakeman and Lambert's 1959 book Voting in Democracies, p. 129-131.

They used six-seat two-party example where the party with the majority of votes had most of its votes gathered in three candidates, and under Hare would have its fourth candidate eliminated, so only able to take three of the seven seats.

under Droop, more of the winners' votes are surplus and when the votes are transferred along party lines, the vote tally of the fourth candidate is brought up, saving him or her from elimination.

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