Mixed Member Proportional (MMP) Representation in New Zealand
Here's Elections New Zealand's explanation of how Parliament is elected.

Here are some government views on the effects of proportional representation:

The new electoral system is expected to make the single-party majority governments to which New Zealand has become accustomed much less likely in the future. A new era of minority and coalition governments is expected to present some significant challenges for the State sector, and especially for the Public Service.

Some additional thoughts:

The Parliaments elected in 1996 and 1999 have higher proportions of MPs who are women (29.2% and 30.8% respectively; 1993 21.2%), Mäori (13.3% in 1996 and 1999; 7.1% in 1993), Pacific Islanders (2.5% in 1996 and 1999; 1% in 1993) and Asian (0.8% in 1996 and 1999; none in 1993). It is notable that most of these improvements in representation have come about through party lists....Voter turnout in 1996 was 3% higher than in 1993, but declined by 3.4% in 1999....First, some people doubt whether New Zealand's multi-party governments since the first MMP election in 1996 have been as effective as the single-party governments it had under FPP since the mid-1930s....Second, some people say they are disappointed that MMP has not brought a new era of political consensus. That was never a realistic possibility since it overlooks the basic realities of democratic politics. MMP has certainly brought more political co-operation and dialogue between parties, but it has also brought more disagreements out into the open.