If all seats are not filled by candidates obtaining quotas by this means, the next preferences of the voters for the least successful candidates are distributed until all the vacant seats are filled. Proportional representation gives minority parties and independent candidates a fair chance of winning some of the last seats to be filled. Voters can make a single mark against a party or independent candidate on their Senate ballot paper. Their preferences are then distributed according to documents lodged by party and independent candidates with the Australian Electoral Commission . Parties pass out 'how to vote' cards so their supporters have a guide to numbering the boxes in ballots.
Political parties can make arrangements about sharing preferences with other parties.
This practice has had an important impact on the outcome of many elections. The media tend to interpret a relatively high 'informal' vote as a protest against the major parties. The minimum voting age was lowered from 21 to 18 in 1973. Parties Major Australian political parties have structured ways to involve their members in developing party policies on issues. Elected politicians rarely vote against their parties in Parliament.