Zipper system

Condorcet methods Positional voting Cardinal voting Quota-remainder methods Approval-based committees Fractional social choice Semi-proportional representation By ballot type Pathological response Strategic voting Paradoxes of majority rule Positive results The zipper system, also known as "vertical parity" or the "zebra system",[1][2] is an electoral mechanism intended to enforce gender parity in countries using party-list proportional representation with closed lists.

[4] More modern variants on the zipper system, based on the fair share sequence, biproportional apportionment, and other rules can enforce gender quotas much more precisely, while introducing less distortion into party lists.

Argentina, Bolivia, Costa Rica, Ecuador, France, Kenya, Lesotho, Libya, Mongolia, Nicaragua, Senegal, South Korea, Tunisia, and Zimbabwe all implement the zipper system in at least one elected body.

[16] Although the zipper system rank-order rule requires a 50–50 split between women and men on party lists, it does not always translate to equality of representation in legislatures.

[4] Some studies have argued both genders tend to be evenly-placed within party lists, making the zipper system unnecessary, but research on this topic is mixed.