Representation - the linkage between citizens and members of parliament - is of paramount interest as legislation affects all areas of citizens' lives. However, "representation" is an elusive concept. How should "representation" be measured? How do institutions shape the relationship between members of parliament and citizens?This study offers a novel approach and dataset to conceptualize and analyze the representation of citizen preferences by parliamentary members. Drawing on the fact that Swiss citizens regularly cast referenda on the same policy proposals that members of parliament vote on, various determinants and consequences of higher or lower congruence between citizen preferences and politicians' votes are analyzed. While the focus is on the design of electoral systems (e.g., majoritarian vs. proportional representation and district magnitude), further analyses include, among others, the relationship between representation and electoral success.englischer Sprache.