There is no such thing as "compulsory voting"

in Downunder. 
It may be that there is in some other parts of the world. Perhaps they stand there with a gun pointed at you and make you vote - but I doubt it.
There is in this country a legal requirement for eligible people to enrol to vote and, having done that, attend a polling booth on polling day. (There are also provisions for postal voting, pre-poll voting and absentee voting.) There is a requirement to take the papers given to you, mark them and place them in the correct ballot boxes.
There is absolutely no requirement that you mark the ballot papers in such a way that might be considered a vote. 
It is, rightly, an offence to discourage people from voting. This is possibly what allows the Electoral Commission and others to make statements like "Remember, voting is compulsory."
There are people who don't vote. They forget. Something happens so they cannot get there. They don't want to vote. They don't understand what they have to do. There are any number of reasons. I didn't vote one year because the Electoral Commission made a mistake - but I did go to a polling booth.  It would not have made any difference to the outcome but I put in a formal complaint and I believe an office procedure was changed as a result. When other people don't go to a polling booth or make other arrangements they sometimes get fined. It is only a very small number of people who don't vote for religious reasons or who are barred from voting.
But I have just read yet another piece about "compulsory voting" and how it makes this country one of the best in the world, how it makes for a fairer outcome and one of the most stable democracies.
I don't believe those things because the vast majority of people vote for the same party all their lives. They have little or no interest in politics or the policies of political parties. They have no idea how we are governed or how government works. 
We may not have to contend with the worries of an out of control President in one country or Brexit in another country but we have other problems - including frequent changes of Prime Minister. We have politicians who are lazy about the political process, especially in their "safe" seats. They may word hard in other ways but they don't need to work to get all votes, just sufficient votes to swing the seat in their favour. We have an entire country which is lazy about democracy and which takes it for granted.
I am not sure that is a good thing.