This thesis consists of four articles
and an introductory section. The main research questions in all the articles
are about proportionality and party success in Europe, at European, national or
district levels. Proportionality in this thesis denotes the proximity of seat
shares parties receive compared to their respective vote shares, after the electoral
system’s allocation process. This proportionality can be measured through numerous
indices that illustrate either the overall proportionality of an electoral
system or a particular election. The correspondence of a single party’s seat
shares to its vote shares can also be measured. The overall proportionality is
essential in three of the articles (1, 2 and 4), where the system’s performance
is studied by means of plots. In article 3, minority party success is measured
by advantage-ratios that reveal single party’s winnings or losses in the votes
to seat allocation process.