Advantages of AV

One advantage of transferring ballots is that it enables the votes of several candidates to accumulate, so that diverse but related interests can be combined to win representation. AV also enables supporters of candidates who have little hope of being elected to influence, via their second and later preferences, the election of a major candidate. For this reason, it is sometimes argued that AV is the best system for promoting centrist politics, as it can compel candidates to seek not only the votes of their own supporters but also the ‘second preferences’ of others. To attract these preferences, candidates must make broadly-based appeals rather than focusing on narrower issues. The experience of AV in Australia tends to support these arguments: the major parties, for example, typically try to strike bargains with minor parties for the second preferences of their supporters prior to an election—a process known as ‘preference swapping’. Furthermore, because of the majority support requirement, AV increases the consent given to elected members, and thus can enhance their perceived legitimacy.

The experience of AV in Papua New Guinea and in Australia suggests that it can provide significant incentives for accommodatory and cooperative politics. In recent years, AV, or its variant the Supplementary Vote, has also been adopted for presidential and mayoral elections in Bosnia, London, and San Francisco.

Disadvantages of AV

Nevertheless, AV also has a number of disadvantages. First, it requires a reasonable degree of literacy and numeracy to be used effectively, and because it operates in single-member districts it can often produce results that are disproportional when compared to PR systems—or even in some cases compared with FPTP. Also, the potential of AV for promoting centrist outcomes is very dependent on underlying social and demographic conditions: while it successfully promoted interethnic accommodation in Papua New Guinea during the 1960s and 1970s, it has been criticized in another Pacific country, Fiji, since it was implemented there in 1997. Moreover, as its use in the Australian Senate from 1919 to 1946 noted, AV does not work well when applied to larger, multi-member districts