Zipper system

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The zipper system (also known as "vertical parity")[1] is a method of drawing up party lists in proportional representation electoral systems. It requires candidates on the list to alternate between men and women in order to secure equal representation in candidacy and potentially elected members.[2]


Some countries mandate the zipper system in their electoral laws. It was introduced in Italy in 1993, but overturned by the constitutional court in 1995.[3] In countries without a legal requirement, parties may choose to implement the zipper system on their own lists, such as the Swedish Social Democratic Party (SAP).[2] The SAP's introduction of the zipper system in 1993 led to 48% of its in the 1994 general elections being female, and contributed to a record number of female MPs being elected to the Riksdag.[2]

Countries using the zipper system
Country Notes
Costa Rica Parties must also alternate between men and women at the top of their lists in different provinces[1]
France For bodies elected by proportional representation[6]
Mauritania Applicable to party lists for constituencies with three or more seats.[9]
Zimbabwe Applicable to Senate elections[13]


  1. ^ a b Gender equality ruling aims for nearly 50/50 male-female Costa Rican legislature The Tico Rimes, 27 May 2016
  2. ^ a b c Electoral Gender Quota Systems and their Implementation in Europe: Update 2013 Directorate-General for Internal Policies
  3. ^ 4. Quotas and Affirmative Action to increase female participation in political life Directorate-General for Research
  4. ^ Where Rwanda and Bolivia Lead the World The Globalist, 10 May 2016
  5. ^ Women in parliament in 2017: The year in review IPU
  6. ^ France IDEA Gender Quotas Database
  7. ^ Lesotho IDEA Gender Quotas Database
  8. ^ Libya IDEA Gender Quotas Database
  9. ^ Al Jamiya-Al-Wataniya (National Assembly) IPU
  10. ^ Nicaragua IDEA Gender Quotas Database
  11. ^ Senegal IDEA Gender Quotas Database
  12. ^ Women's political participation in Tunisia Euspring
  13. ^ Zimbabwe IDEA Gender Quotas Database