As the “Short Twentieth Century” came to an end, more and more democracies seriously considered the possibility –often for the first time in their history- of changing their national electoral system. Since then, the total number of electoral reforms enacted in countries that select their rulers through free and fair elections has sharply increased: in the last two decades over 33% of the world’s democratic states modified the formula employed for choosing the members of their national legislatures, and a similar percentage adjusted other elements of the rules of the game such as the district magnitude, the legal threshold, the assembly size or the ballot structure. Unfortunately, the academic examination of the causes and consequences of t...