Right now, our country is chopped up into 338 districts called electoral districts or ridings. In each of these ridings, candidates are nominated by their parties to run so that they can be the MP from that riding.
On election day (or at advance polls), we go to the polling place and we mark an X beside the name of the person we want to elect. Our ballot has a list of names and the party affiliation of the candidate.
The candidate who gets the most votes, wins, and becomes the Member of Parliament for that riding. The other candidates go back to their previous lives and have no role to play in the new government.
The challenge we have with this system, is that for everyone who voted for the other candidates, their vote is wasted and doesn’t count. In some ridings, a candidate can win with 30% of the vote, leaving 70% of the voters to be frustrated.
The goal of a proportional system is to try to get as many votes as possible represented in the House of Commons. So, if 30% of the people voted for a particular party, then that party should have roughly 30% of the seats.
The current system tends to distort the numbers so that large parties end up with more seats than their proportion. In the last election in 2015, the Liberals received 39.5% of the votes in Canada and were awarded 54.4% of the seats. They ended up with about 50 more seats than they would have deserved under a proportional system. All the other parties received fewer seats.
The net result of this particular power imbalance is that the current government enjoys a majority of the power while not representing a majority of Canadians. This was true in the previous election as well. In fact the last time that there was a true majority was the election of PM Mulroney in 1984.
The mathematics are such that a small swing in popular vote can result in a massive swing in composition of Parliament. The dramatic change between the Parliament of 2011 under PM Harper and the 2015 Parliament under Trudeau demonstrates this. There was definitely a change in public support, but the change was smaller than you would think by looking at the final resulting seat counts.