Coexistence (electoral systems) explained

In political science, coexistence^[1] involves different voters using different electoral systems depending on which electoral district they belong to.^[2] This is distinct from other mixed electoral systems that use parallel voting (superposition) or compensatory voting. For example, the rural-urban proportional (RUP) proposal for British Columbia involved the use of a fully proportional system of list-PR or STV in urban regions, combined with MMP in rural regions.^[3]

Coexistence of electoral systems exist in multiple countries, like the Democratic Republic of the Congo and Panama, as well as for elections of the European Parliament.. Historically, variants have been used in Iceland (1946–1959), Niger (1993, 1995) and Madagascar (1998).^[4]

Types of coexistence

!Type!System!Example(s) for use
Coexistence	e.g. FPTP/SMP in single-member districts, list-PR in multi-member districts	Democratic Republic of the Congo, Panama
Supermixed	e.g. FPTP/SMP in single-member districts, conditional party block voting in multi-member districts	Cameroon, Chad
	Rural-urban proportional representation (RUP)	Denmark (formerly), Iceland (formerly)
	Seat linkage compensatory mixed system (MMP) and FPTP in special consituencies	Bolivia

References

Massicotte & Blais . 1999 . Mixed electoral systems: a conceptual and empirical survey . Electoral Studies . 18 . 3 . 341–366 . 10.1016/S0261-3794(98)00063-8.
Herron . Erik S . Nishikawa . Misa . 2001-03-01 . Contamination effects and the number of parties in mixed-superposition electoral systems . Electoral Studies . 20 . 1 . 63–86 . 10.1016/S0261-3794(00)00002-0 . 0261-3794.
In Search of Compensatory Mixed Electoral System for Québec . Massicotte . Louis . 2004.
Golder . Matt . 2005-03-01 . Democratic electoral systems around the world, 1946–2000 . Electoral Studies . 24 . 1 . 103–121 . 10.1016/j.electstud.2004.02.008 . 0261-3794.