ABSTRACT
In a simplified manner, we can use the number of parties with at least 3 percent of the seats to distinguish between three overall categories: twoparty systems (P3%S of two), moderate multiparty systems (P3%S of three to five), and extreme multiparty systems (P3%S of more than five). The breakpoints here thus follow Sartori's (1976) analysis of fragmentation. However, with additional factors we are able to thus expand the categories into more precise situations. In this analysis a party system is thus considered one of eight different types, depending on various mathematical results in an election or series of elections. A polity may thus go through, or shift among, various party systems over time, or its party system may remain constant throughout the period under study. Certainly a party system that is the output of only one election cannot be considered durable, unless we are looking at the most recent elections in which case it might have some durability. Thus, earlier single-election party systems should either be seen as deviant (if the polity then goes back to the old party system) or transitional (if the polity then goes on to a new party system for at least a couple of elections). In the data following, such single-election party systems are indicated with square brackets.
