The charts prepared for the article “Measures of Differentiation among Candidates as an Indicator of the Quality of Voting Advice Applications”: https://docs.google.com/document/d/1KVTso9cdwvCxhPC3bEp8rAEY_7v3gWvCzHNYVOjcMR8/edit
Includes Wahl-O-Mat (Germany) 2005, 2009, 2013; StemWijzer (Netherlands) 2006, 2010, 2012; and Volební kalkulačka (Czech Republic) 2013