The mechanical and psychological effects of electoral systems: A quasi-experimental study

Having two votes for the same election or two simultaneous elections with different electoral systems provides a golden opportunity to ascertain the impact of the electoral system and to sort out the relative magnitude of mechanical and psychological effects on parties and voters. The authors propose a new methodology for estimating such effects and apply that methodology to 13 elections, 9 in Switzerland and 4 in Japan. The authors find mechanical effects to dominate in half of the elections examined, most particularly in the more recent Swiss elections. They discuss the implications of these findings.