Parallel Voting System

A parallel voting system, also called a mixed-member majoritarian (MMM) system, combines two electoral formulas operating side by side. Voters typically cast two ballots: one for a candidate in a single-member district (decided by plurality or majority), and one for a political party on a closed or open list allocated by proportional representation. Crucially, the two tiers are calculated independently—a party's list seats are not adjusted to compensate for over- or under-representation won in the district tier.

This distinguishes parallel voting from mixed-member proportional (MMP) systems such as Germany's or New Zealand's, where list seats top up district results to make the overall chamber proportional. Because there is no compensation, parallel systems tend to favor larger parties and produce outcomes closer to the majoritarian tier than to pure PR, though smaller parties can still win list seats they would not win in districts alone.

The ratio between tiers varies widely. Japan's House of Representatives, reformed in 1994, elects 289 members from single-member districts and 176 from regional PR blocs. Russia uses a 225/225 split for the State Duma (when the mixed system is in force, as restored in 2016). South Korea, Lithuania, Taiwan, the Philippines, and Senegal also use variants of parallel voting, though tier sizes and ballot structures differ.

Supporters argue parallel systems retain a direct constituency link while injecting some proportionality and allowing minor parties a foothold. Critics note that disproportionality remains substantial, that two classes of legislator are created (district vs. list), and that strategic "decoy list" tactics—where a dominant party encourages allies to run separately on the list side—can distort results, as observed in some Italian and Japanese elections.

For MUN delegates analyzing democratic design, the key contrast to remember is parallel = no linkage; MMP = compensatory linkage.