Is invalid voting more common in complex electoral systems than in simpler ones? An examination of mixed systems and first-past-the-post systems

Abstract This study examines the level of invalid voting in mixed electoral systems in comparison with the level of such voting in First-Past-The-Post (FPTP) systems. High levels of invalid votes can indicate problems with the electoral system used and can weaken the legitimacy of elections. Theoretically, a higher level of invalid votes can be linked to elections in which a complex electoral system, such as a mixed system, is used. Conversely, lower levels of invalid voting can be linked to elections in which a simple electoral system, such as a FPTP system, is used. We carry out a large, global, cross-national empirical comparison of invalid voting for national parliaments worldwide that covers more than six decades. First, we examine whether the level of invalid voting is higher in mixed systems than in FPTP systems. Second, we examine whether the level is higher in countries that currently use mixed systems but previously used FPTP systems or were formerly non-independent states. The results show that invalid voting is more prevalent in mixed systems than in FPTP systems. They also illustrate that invalid voting is more prevalent when countries transition from a FPTP system to a mixed electoral system, or when they adopt a mixed system following full independence or the restoration of sovereignty. In the persistent debate about which electoral system is preferable, invalid voting rates represent one of several indicators of system quality, and according to this measure, FPTP systems outperform mixed systems.