The pros and cons of Canada's first-past-the-post electoral system

As part of his 32-point plan to "restore democracy," Liberal Leader Justin Trudeau said Tuesday that if elected, he would create a special, all-party parliamentary committee to study alternatives to the current first-past-the-post (FPTP) electoral system, including ranked ballots, proportional representation, mandatory voting and online voting.

• Justin Trudeau vows to end 1st-past-the-post voting in platform speech

Here are some things to know about first-past-the-post:

How does Canada's FPTP voting system work?

In every riding, the candidate that wins the highest number of votes wins the right to represent that particular seat in the House of Commons.

The winner does not need an absolute majority — i.e., more than 50 per cent of the votes cast in the riding.

Why do some people have a problem with that?

It means many candidates win their seats with less than 50 per cent of the votes.

It also means two people running in different ridings can each earn the same percentage of the vote but one may win while the other does not.

The first-past-the-post system can also encourage what some call tactical voting — casting a ballot not for the person you want to vote for, but for the candidate best positioned to defeat the candidate you most dislike.

What is one popular alternative?

It's called proportional representation, and it would benefit smaller parties that win a respectable share of the overall votes cast in the country, but can't quite eke out a first-place finish in a particular riding to win an actual seat in the House of Commons.

There are a variety of PR models but the objective is to make a party's share of seats in the Commons equal to their slice of the popular vote.

Generally, PR involves electing multiple members in each district, with seats assigned according to each party's share of the vote in that district.

What makes this an issue in Canada?

There are a lot more political parties in Canada than you might think.

Elections Canada says there were 18 political parties registered in 2011, down from the all-time high of 19 in 2008.

In 1972, just four parties were registered.

There was an average of five candidates per riding in the 2011 election, with as few as three and as many as nine in any given riding.

Consequently, dividing up Commons according to each party's share of the vote would make it more difficult for any one party to amass a majority of seats.

Experts suggest first-past-the-post provides for more stability whereas PR would likely result in more coalition governments.

Governing by coalition — when multiple parties come together to pool their resources and form a plurality — is the status quo in a number of countries around the world, most notably Israel.