The paper offers a macroscopic view of the legislative electoral formulas in force in 166 sovereign countries, whether democratic or not. The purpose is to determine which formulas are the most widespread, and whether the prevalence of a formula is correlated with geographical, historical, economic, and political factors. While plurality and PR systems are equally frequent, the former tend to be found in more populated countries. PR prevails in Europe and South America, and among the most democratic countries, while the plurality rule is more typical of Asia, Africa, and North America, and is especially popular among former British colonies. Large countries are more likely to opt for single-member districts. No significant correlation emerges between the level of economic development or French colonial background and any electoral formula. The study suggests that the selection of an electoral system is not merely the outcome of party interest, but is also strongly influenced by ideas about what is good, just, or efficient.
