Compulsory voting
, 22 countries were recorded as having compulsory voting. Of these, only 10 countries (additionally one Swiss canton and one Indian state) enforce it. Of the 30 member states of the Organisation for Economic Co-operation and Development, 10 had forms of compulsory voting.
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.