There are a number of formulas for allocating seats to parties in proportional voting systems. All are variations on either the 'highest average' or 'least remainder' principles. The choice of allocation method doesn't make much difference to the overall outcome, but some methods discriminate against smaller parties.
The Webster/Ste. Lague method is the most proportional system, so I see no reason to consider any other.
For those interested in the truly arcane, you can begin your study of allocation formulas with this excellent article by Mike Ossipoff:
Allocation Formulas for party List PR
There are a number of ways of measuring distortion. I hope this one is simple and easy to understand.
Distortion for each party is calculated by subtracting their Vote Percentage from their Seat Percentage.
For example, if a party gets 100% of the seats with 60% of the votes, then the distortion is +40. If a party gets 12% of the votes and 0% of the seats, then the distortion is -12.
Positive values indicate that the party is over-represented. Negative values indicate that the party is under-repesented.
Of course, when one party has a member too many, that means that some other party has one member too few.
Every positive distortion for one party is also a negative distortion for another party. If you add up all the distortion factors, the total is always 0. So, how do we calculate the total distortion in the system?
One way is to add up the absolute values of the distortion factors for each party. But now each distortion is counted twice.
So, to calculate the Index of Distortion for each riding, and for the province, we add up the absolute value of the distortion factors for each party, and divide by 2.
For the overall election results, values under 4 are usually considered acceptable. Values between 4 and 8 are marginal. Values over 8 cannot be considered truly proportional.
A 'Quota' is the number of votes required to elect a member.
The quota is defined differently in different voting systems.
Throughout the Amazing Proportional Representation Simulator, 'quota' means a Hare Quota, the number of votes cast, divided by the number of members to be elected.
To find out more about electoral quotas and different voting systems, visit these fine websites:
Ace ProjectThe 'Threshold' is the minimum percentage of votes a party must get in order to win its first seat.
Every system has an inherent threshold, which depends on the number of candidates and the number to be elected. For example, in a plurality system such as we now use in Canada, if there are 2 candidates, and only 1 to be elected, a candidate requires 50% plus 1 to be elected. However, if there are 3 candidates, and 1 to be elected, a candidate with 1/3 of the votes plus 1 can get elected if the other votes are evenly split.
In our current multiparty, single-member plurality system, it is not uncommon for candidates to be elected with less than 30% of the votes in their riding. The remainder of the votes in the riding do not help to elect anyone, and are therefore 'wasted'.
In multimember ridings, the math gets more complicated, but the minimum number of votes required to get elected is usually about half a quota, which is the number of votes cast, divided by the number of members to be elected. In other words, in a three-member riding, a candidate will need at least about 16% of the votes to get elected. In a seven-member riding, a candidate will need at least about 7% of the votes cast in the riding to be elected.
Our province-wide compensatory list will elect a member for any party which gets at least about .5% of the votes cast in the province, unless they have 'used up' their votes by electing a member in a riding.
In some jurisdictions, an arbitrary threshold is imposed to make it harder for small parties to win seats in the legislature. For example, in Germany and in New Zealand, a party cannot win list seats unless they get at least 5% of the votes nationally, or unless they win at least one riding.
In the Netherlands, the legal threshold is one quota, which, since they elect 150 members from a national list, is .67% of the votes cast in the country.
Under the First Past The Post voting system which we now use in Canada, if you vote for a winning candidate, your vote gets you a representative in Parliament.
However, if you vote for a losing candidate, your vote gets you nothing. In fact, it really doesn't count at all.
Unfortunately, under our current system, most of us vote for people who do not get elected, most of the time. Our votes are 'wasted'.
In a fair voting system, everyone gets the best representation possible, because every vote counts.