A review of systems around the world which use proportional representation systems on average elect 8% more women. There are a number of factors which influence MMP ’s ability to help elect more women and diverse under-represented groups.
Here are 3 of the main factors...
1 - PR is more likely to produce coalition governments.
Local research has shown that women candidates and potential candidates will often choose not to run for public office because of the discomfort of negative campaign tactics. Women, diverse women, and members of diverse groups may face unequal exposure to personal attacks during campaigns due to sexism, racism, ableism, and other forms of discrimination. However, given the need for greater collaboration amongst parties in coalition governments, this would promote a decrease in partisan attacks in campaigns and would reduce rewards of negative campaigning.
Some women have described combative legislatures as a barrier to running. However, coalition governments increase the likelihood of collaborative approaches being needed to advance an agenda in the legislature.
2 - MMP tends to provide greater opportunity for small parties to gain elected seats.
In PEI, smaller parties have historically tended to nominate more women, more diverse women, and more diverse candidates overall than the two main parties.
3 - MMP would require changes to the nomination process which would increase the chances of women being nominated.
When parties nominate nine candidates, they will more likely nominate a balanced and diverse slate than when they nominate just one. That’s why 36% of the members of the Scottish Parliament are women, compared to less than 20% on PEI.
Local research has shown that the biggest challenge for women is not "getting support at the polls" - it’s getting their name on the ballot in the first place. MMP would nominate district candidates in the usual way, district by district, but it would require changes to the nomination process in that there would also be a province-wide list of candidates for each party, nominated in a province-wide process. It is easier for parties to mandate gender parity or increased diversity on a list than in district-by-district contests.
MMP’s nomination process includes a list, which has been shown in other places to increase opportunities for gender balance and increased diversity across the slate of candidates.
This is due to “contagion” effect, recognized by academics who study electoral systems: Voters expect a diverse list of candidates. Parties can easily compare lists, so the pressure to put forward a diverse list is “contagious.” When one party starts putting forward more women candidates, other parties feel compelled to do the same, fearing that they may lose voters if they don’t. (On PEI, th same applies to rural and regional diversity.) District-by-district nominations are not as susceptible to this “contagion.” (Matland and Studlar 1996)