ABSTRACT
This chapter constitutes an attempt to delve into the sources of party system institutionalization (PSI) in general, trying to understand which factors contribute to hindering this process in particular. It describes the conceptualization and the operationalization of PSI. In an attempt to complete part of Mair's unfinished work, this chapter evaluates various explanations of the variations in institutionalization observed in seven new post-authoritarian party systems in the Black Sea region. Adapting Pedersen's well-known index of electoral volatility, he designed the index of government alternation (IGA), which adds the net change in percentage of ministers gained and lost by each party from one government to the next and then divides by two, to measure the degree to which governing alternations are partial wholesale. In summary, most of the arguments suggested in Casal Baertoa and Mair have been confirmed: party system institutionalization is higher in systems with strong party institutionalization, high legislative concentration, cleavage cumulation and parliamentarism.
