I found this article very interesting:
"The disquiet engendered by these results led the Labour government elected in mid-1984 to establish a Royal Commission on the Electoral System. Its 1986 report, Towards a Better Democracy, recommended the adoption of a voting system similar to Germany’s. The commission argued strongly that, on the basis of the ten criteria it had established for judging voting systems, MMP was ‘to be preferred to all other systems’.
Neither of New Zealand’s major parties favoured the proposal and the matter might have died had the National Party’s 1990 election manifesto not promised a referendum on the topic. In an initial referendum, held in 1992, nearly 85 per cent of voters opted ‘for a change to the voting system’; 14 months later, the new electoral system was adopted after a second referendum in which 54 per cent favoured MMP (while 46 per cent voted to retain FPTP).
As in Germany, in parliamentary elections in New Zealand the electors have two votes—one for a political party (called the party vote in New Zealand) in a nationwide constituency, and one for a candidate in a single-member district. Whereas representatives for single-member districts (called electorates in New Zealand) are elected by FPTP, the overall share of the seats in Parliament allocated to political parties stems directly from and is in proportion to the number of party votes they receive. If a party wins 25 per cent of the party votes, it will be entitled to (roughly) a quarter of all the seats in the 120-member Parliament, that is, about 30 seats. If a party that is entitled to a total of 30 seats has already won 23 electorate seats, then it will be given another seven seats drawn from the rank-ordered candidates on its party list who have not already been elected in a single-member district. Likewise, if a party entitled to 30 seats has won only 11 single-member district seats, then it will acquire another 19 MPs from its party list.
There are two thresholds for MMP in New Zealand.
To win a share of the seats in Parliament based on the party votes, a party must either win at least 5 per cent of all the party votes cast in a general election or win at least one single-member district seat.
In the 1996 general election, five parties crossed the 5 per cent threshold and one won a single-member district seat but did not clear the 5 per cent threshold. Three years later, five parties again cleared the 5 per cent threshold. Two other parties failed to do so but won single-member district seats, which qualified one of them for an additional four seats in Parliament (it had won 4.3 per cent of the party votes cast in the election).
In the 2002 general election, six parties cleared the 5 per cent party vote hurdle, and a seventh party won a single-member district seat that enabled it to bring one other person into Parliament from the party’s list.
These figures point to one major change caused by the introduction of MMP.
Established, at least in part, to ensure ‘fairness between political parties’, the new voting system has seen the index of disproportionality plummet from an average of 11 per cent for the 17 FPTP elections held between 1946 and 1993, to an average of 3 per cent for the first three MMP elections. Every FPTP election in New Zealand from 1935 until 1993 saw one of the country’s two larger parties—Labour or National—gain an absolute majority in the House of Representatives. One consequence of MMP has been that, in the three elections to date, no single party has won more than half the seats in Parliament. In 1996, the largest party won 44 out of the 120 seats; in 1999 the largest party won 49 seats; and in 2002 the largest party won 52 seats.
Not surprisingly, then, New Zealand has changed from being a country accustomed to single-party majority governments to being a country governed by coalitions.
After the first MMP election, two parties formed a coalition government that commanded a small majority (61 out of 120 seats) in Parliament. Since that coalition disintegrated in August 1998, New Zealand has had minority coalition governments that have had to rely on either formal or informal supporting arrangements (negotiated with other parties or, on occasion, with individual MPs) to ensure that their legislative programmes have been able to win majorities in Parliament.
One of the other criteria used by the Royal Commission on the Electoral System was ‘effective government’. The commission noted that electoral systems should ‘allow governments ... to meet their responsibilities. Governments should have the ability to act decisively when that is appropriate’.
In this regard it should be stressed that MMP governments in New Zealand have had little trouble governing: all have had their budgets passed without any real difficulty, and none has faced the likelihood of defeat in a parliamentary vote of no confidence. At the same time, New Zealand parliaments have fulfilled another of the royal commission’s criteria by also becoming more effective. Governments can no longer rely on (indeed, they seldom have) majorities on parliamentary committees, and there is a far greater degree of consultation—of give and take—between government and opposition parties in MMP parliaments."
What I could not find is how other countries have sold the concept of proportional representation to voters. Anyone have any ideas or sources on this topic?