Ok...I can see I need to research more about "Preferential voting" and 'proportional representation'.

Here's a start, Bill, cobbled together from some of my past posts and the instructions I included in the constitution of the local bushfire brigade we formed. It's a bit long but it's pretty complete and relatively simple to follow.

In Oz, Preferential voting is used for lower house seats and Proportional representation with a Preferential distribution of votes is used for upper house seats; Tasmania uses it for its lower house seats as well.

PREFERENTIAL VOTING SYSTEM

VOTING PROCEDURE
Each voter shall indicate their decreasing order of preference for candidates on the ballot paper by placing the number 1 against the name of the candidate of their first choice, the number 2 against the name of the candidate of their second choice, and so on until every candidate has a preference number against their name. Each ballot paper so completed is a formal vote: ballot papers not conforming to this description are declared informal and invalid by the Returning Officer.

COUNTING PROCEDURE
The Returning Officer shall sort the ballot papers into piles; one pile for each candidate given a formal vote and one pile for informal votes. The Returning Officer shall then count the number of papers in each pile to ensure that the total number adds up to the number of votes cast. Ballot papers containing informal votes play no further part in the election.

Any candidate who has received more than half the first preferred choices is declared elected.

Where no candidate receives more than half the first preferred choices the candidate with the lowest number of first preferred choices is eliminated and that candidate's ballot papers are distributed among the other candidates according to the second preferred choice on each ballot paper. Where this procedure gives any candidate more than half the total formal votes cast, that candidate is declared elected. Where no candidate receives more than half the total formal votes cast, the candidate with the next lowest number of first preferred choices is eliminated and that candidate's ballot papers are distributed among the other candidates according to the next preferred choice shown on each ballot paper. This redistribution of ballot papers is continued until a candidate's pile has more than half of the total formal votes cast; that candidate is declared elected.

There is also, in some states, the Optional Preferential system of casting ballots. The Ballot paper is divided (usually by a horizontal line near the top) into two sections. "Above the line" there is only the full list of parties standing. The boxes are given numbered preferences by the voter (following the rules outlined above) and the distribution of preferences between them is conducted by the Returning Officer according to formal deals arranged between the parties and registered with the Returning Officer before Voting Day. "Below the line" there is the full list of candidates. If you wish to cast your vote here the procedure outlined above is followed for both casting and counting.

PROPORTIONAL REPRESENTATION
This is used in the Senate and all State Upper Houses (Queensland has no upper house) and for each of the five electorates in Tasmania's Lower House, where it is known as the Hore-Clark System. At each Commonwealth election (where, usually, half the Senate is up for election; 6 seats for each State) a quota (required for a candidate's success) is 1/6th of the vote for that State.

When a candidate has achieved enough primary votes to complete a quota, they are declared elected (after all challenges to counting have been resolved) and their excess primary votes distributed to the second ranking candidate in their party. In a situation where there are two dominant parties, this will usually ensure that each gets their top two candidates elected. Minor parties are more easily able to collect a quota in such elections because all they have to accrue is 1/6th of the voters for that state. It's after this that the fun starts. Those candidates whose primaries don't add up to a complete quota have their ballot papers redistributed according to the Preferential System outlined above until all quotas have been allocated.

Once again, where there is Optional Preferential voting, you have "Above the line" and "Below the line" options to cast your vote.

In Commonwealth elections when there has been a Double Dissolution (triggered by a situation where the Senate has twice rejected the same Bill passed to it by the House of Reps, forming a "trigger" that allows the Prime Minister to call such an election), the whole Senate (12 seats for each State) is up for election and a quota is 1/12th of the vote for that State.

It is rare for candidates from minor parties to get up for a seat in the lower house (even with distribution of preferences) but minor parties have more success in the Senate, especially if it's a Double Dissolution. Immediately after the election following a Double Dissolution, the Senate sits with the House of Reps and the rejected Bill(s) is/are put to the combined mob, ensuring a political resolution to a what otherwise would be seen as a Constitutional quandary.

The advantage of both Preferential voting and proportional representation is that they more easily allow minor parties to "get up" than does "first past the post" voting.   The disadvantage is that there will usually be a few seats in the lower house that cannot be decided by the close of counting in the late evening of Voting Day; seats where the count is very close between candidates can be determined by the arrival of the post. In SA a few years ago, the deciding votes for the seat that gave control of the Legislative Assembly (the name for all the State Lower Houses) were said to be "coming down the dog fence in the saddle bags of a boundary rider". The more complex possibilities in the Senate mean the final Declaration of the Poll may take a couple of weeks; in a close election that keeps everyone on their seats, especially if a maverick gets up in the last remaining quota for one or more states as happened in Victoria recently.

COMPULSORY VOTING
My own preference is for compulsory voting, as it forces everyone to take some level of responsibility for the consequences. I realise that many duck any notion of responsibility in this matter and can even express it on the ballot papers. If you just number them in consecutive order down the list, it's counted as valid but is called a "donkey vote"; their proportion of the total is mulled over by psephologists. If you mark any part of the ballot paper outside the boxes (by writing derisive insults, for example) or use comments in the boxes, the ballot paper is classified "Invalid" and not counted to any candidate; the proportion of these in the total is described as "the protest vote" and is also mulled over by psephologists.

Many of my American friends who thought compulsory voting was a generally good idea were not so sure when I told them that this meant that Australians were required to inform the Australian Electoral Commission (an arm of the Commonwealth Govt also used by State and Municipal Govts) of any change of address. The independence of the AEC ensured no nonsenses of the types we heard about a couple of years ago but they had to have a record (in the public domain) of where to mail the notification if you were to be fined.

I'm not sure compulsory voting, compared with noncompulsory voting, would give a great difference in the results but I think it would certainly change the tactics used by both politicians and voters. I regard myself as unwilling to allow any arm of govt to arrogate to itself any responsibility I think I should exercise. I want to vote and I construct my tactics accordingly and then go and vote, even when I have to list 163 candidates in descending order of preference on a ballot paper the size of a decent tablecloth.