[amenhotep]

Which is, incidentally, the exact same way you do it in a non-compulsory voting system. Spoiled ballot is a signal that you cared enough to get off your arse and vote and deliberately chose none of the candidates, so you might be reachable with the right message. Not voting is just a signal of general apathy, not very tempting to engage with.

63.9% turnout is just business as usual, but - if you ask me - 36.1% of ballots being spoiled would precipitate a sea change in the political landscape.

[jfengel]

There are other reasons for not voting besides apathy. Many people would like to vote but are deterred for a variety of reasons: they have to work, or take care of children, or they're afraid of being arrested. A common tactic is to put up posters telling people that they can't vote if they owe child support.

An alternative would be a national holiday rather than mandatory voting. Either way, I'd like to see voting made easier.