CSES (CSES1, CSES2, CSES3, CSES4, and CSES5) is a collaborative program of research among election study teams from around the world. Participating countries include a common module of survey questions in their post-election studies. The resulting data are deposited along with voting, demographic, district, and macro variables. The studies are then merged into a single, free, public dataset for use in comparative study and cross-level analysis. The research agenda, questionnaires, and study design are developed by an international committee of leading scholars of electoral politics and political science. The design is implemented in each country by their foremost social scientists.

Note: Portugal 2002 from the initial data Module 1 was excluded, as this module provides data until 2001, therefore these observations are coded incorrectly.