Compulsory voting
Compulsory voting is an effect of laws which require eligible citizens to register and vote in elections, and may impose penalties on those who fail to do so. , 22 countries provide for compulsory voting, and 11 democracies — about 5% of all United Nations members — enforce it.
Instant-runoff voting
Because the ballot marking is more complex, there can be an increase in spoiled ballots. In Australia, voters are required to write a number beside every candidate, and the rate of spoiled ballots can be five times higher than plurality voting elections. Since Australia has compulsory voting, however, it is difficult to tell how many ballots are deliberately spoiled. Where complete rankings are not required, a ballot may become exhausted if none of the ranked choices on that ballot advance to the next round.