Is there a decline of democracy in the EU between 2004 and 2016? The relevance of data selection: a replication study of Smolka (2021) and comparison of democracy measures

Is there a Decline of Democracy? Democracy measurement provides the basis for answering this question. However, there are different measurement tools based on different meanings of democracy that have been shown to vary in their concept validity. Therefore, it is relevant to examine whether the results of the different measurement tools converge or diverge with respect to a potential decline of democracy. Smolka (2021) finds a decline of democracy for new and old EU states based on standardized data from the Democracy Barometer. A re-analysis using the original data of the Democracy Barometer and the Democracy Matrix can hardly replicate these results. A comparison of further measurements shows that the instruments diverge rather than converge. I therefore conclude with some thoughts on overcoming the selection problem that arises in light of these contrasts