In the up-coming elections in Ireland (local and EU Parliament), we will take our ballot papers and put numbers beside the names of those we want elected in order of our preference: 1 for the person we most want elected, 2 for our next preference, 3 for the next, etc.. For your ballot to be considered valid, you need only enter a 1, leaving the others blank. You can also add numbers to as many candidates as you want, even to fill out the whole paper.

I strongly encourage everyone to fill out the whole paper, because, when you do, not only are you declaring who you would like to be elected, you're also affirming who it is that you definitely don't want elected.

They're called "preferences", but where you're benefiting the people you give your higher preferences to, if you fill out the whole ballot paper, you're also disadvantaging those you don't want elected.

Imagine an election where there are 13 candidates running.

When I go to vote, I am usually sure of two things: who it is I would like to see elected, and who it is I certainly would not like to see elected. I start filling my ballot paper by putting in my 1, 2, and 3 in reducing order of preference, and then my 13, 12 and 11, in reducing order of distaste.

I then complete the ballot by looking at the rest, and putting in the 4, 5, 6, 7, 8, 9 and 10 preferences, joining the preferred half to the objectionable half with that candidate I care least about either way.

I have a goal: I definitely don't ever want the person who gets my thirteenth preference to benefit from my vote, and by filling out the full ballot, I make sure of this: my ballot may land on many piles as it gets transfered from candidate to candidate¹, but it won't reach the pile of the candidate I put down as my thirteenth preference before the count is over.

If, however, I give "preferences" only to the first 6 people I like, it may result that my ballot eventually can't be transferred to someone, and will be removed from the counting. This will reduce the power of my vote, and will increase every (remaining) candidate's chance of being elected, because my vote won't go to someone else.

When all the ballots are being counted the following happens during the "first count":

1. Each ballot box is opened and its ballots spilled out onto a table.
2. Those counting the votes – the tabulators – will open each folded ballot and look for which candidate has the highest preference.
3. The ballot is placed onto a pile of other ballots for that candidate.
4. If the preference can't be determined from the ballot, the ballot is deemed to be invalid ("spoiled"), and placed onto a pile for these².
5. Once all the ballot boxes have been opened, and all the ballots are put into their respective piles, the counting starts properly.
6. Once all the counting has finished the following pieces of information are known:
   • How many ballots were cast (though this is may already be known from the marked registers at the polling places – I'm not certain)
   • How many ballots were spoiled.
   • Thus, how many ballots were deemed valid (cast ballots minus the invalid ballots).

   • Once it's known how many valid ballots there were, it can be determined how many votes a candidate needs to be elected. This is called the "quota", and is calculated as the number of valid ballots divided by the number of seats to be filled plus one, and then 1 added to the result:

     quota = (no. valid ballots / ( no. seats + 1 )) + 1
     

     So, if there's only 1 seat to be filled, and 50,000 valid ballots, the quota is 25,001 (a.k.a. "50% plus 1", or (50000/(1+1))+1). If there are 4 seats, and 100,000 valid ballots, the quota will be 20,001 ((100000/(4+1))+1). And so on.

7. Of course, at this point, it's also known what the first-preference vote count is for all the candidates, and all this information is announced at the end of the first count.

Based on the above a few things can happen:

• If one or more candidates have more votes than the quota, these candidates are deemed elected.
• If no candidate is elected, then one or more of the worst performing candidates are eliminated, removing them from further consideration/counting.
• A combination of the above two things happens, following rules about how many votes can be transferred.

It's the transferring of the votes that's what makes this whole process cool.

If a candidate is elected at the end of the count, that person has more votes than was needed to be elected (unless the candidate was extremely lucky). The number of votes over the quota is called the "surplus". This number of ballots, selected at random, is removed from the candidate's piles of ballots, and the next preference in each ballot is considered. The tabulator will make one of three decisions:

• If the next preference on the ballot hasn't been elimintated, the ballot is placed onto that candidate's pile.
• If the next preference has been eliminated, the tabulator looks at the preference after that, and continues to look until a preference can be found for a candidate that hasn't been elimintated.
• If such a candidate can't be found, then the ballot is removed from consideration.

The fewer preferences in the ballot (e.g. the voter cast only a 1, or only a 1, 2, and 3, on a 13-candidate ballot), the more likely the ballot will be removed from the counting. When this happens, the ballot has lost all power.

As an aside, a ballot that can no longer be transferred is still a valid ballot, and so the quota doesn't change.

In the case of a candidate being eliminated, all of the ballots for that the candidate are transferred in this way, not just a random selection. So, if your first preference was for someone who gets elected, then there's only a chance (even if it's a good chance!) that your ballot will be considered for a transfer, if your preference is for a candidate who gets eliminated, then your ballot is guaranteed to be considered!

If, though, your ballot can't be transfered, and – for example – the last seat comes down to a 1-vote difference between someone you really don't like, who has the advantage, and someone you're not too pushed about, your ballot can't influence the result, and the person you don't like will be elected.

Bummer.

However, if you had filled out the ballot completely, giving the person you don't like a worst preference than that candidate you're not too pushed about, then your ballot may well be with the person you're not too pushed about, and it's down to an exact tie. And if there's one other person who made the same decision as you, then the person you don't like loses by 1 vote, and doesn't get elected.

Result!

Yes. You can of course argue that the chances of it happening just like this, and of your vote making such a difference, are extremely remote. And, in a strict sense, you'd be right. But you can't argue that it could never happen, or that it could never happen with your ballot.

Think about this: It takes a similar amount of time (and mental effort in some cases!) to fill out a lottery ticket, to try to beat extremely low odds of winning a massive prize, but people still do it. Your vote counts, and it may very well count in such a tight scenario; there's such a low cost to filling out your ballot in this way, it's hard to see that is isn't worth it.

Give preferences to all candidates on the ballot, and know that in the same way that you are voting for the people you give your higher preferences to, you're also voting against those who get your lowest preferences.