The natural starting point of any analysis of electoral systems’ effect on inclusion/exclusion of parties from access to parliament is the “Duverger’s law”. It states that majority/plurality system “tends to party dualism” while “proportional representation tend to multipartyism”. The law is not without exceptions and can be understood only as a probabilistic generalization. Sometimes significant disparities exist within one and the same system-family. Nonetheless, the choice of a type of electoral system (majority/plurality, combined, proportional) is an important general threshold; it is itself a mechanism with an important general impact on minor party exclusion/inclusion and, consequently, party fragmentation. Party systems will be more competitive and fragmented in proportional systems (PS), whereas majority/plurality systems (MS) will usually restrict opportunities for minor parties. Thus, a study of electoral systems worldwide found that “the mean number of parliamentary parties (based on the simplest definition of parties holding at least one seat) was 5.22 in the countries using majority/plurality systems, 8.85 in combined (or mixed) systems, and 9.25 in societies with proportional representational electoral systems.” Similarly, “the mean number of relevant parties [] (holding over 3% of parliamentary seats) was 3.33 in all majority/plurality systems, 4.52 for combined systems, and 4.74 for all proportional systems”.