All final merger decisions by the European Commission from 1990 to 2019 are analysed using a novel dataset containing information about 6245 merger cases from all economic sectors and encompassing all types of decisions, including withdrawn and prohibited cases. Text analysis techniques such as keyness analysis and a dictionary approach are employed to identify trends, showing that terms associated with the More Economic Approach (MEA) have been increasingly used, whereas the concept of dominance has declined since 2004. The tonality of decision documents is found to be predominantly positive, particularly for cleared cases, and varies under different merger regulatory frameworks. Differences in the usage of competition-related terms are accounted for, and ordinary least squares and logit regressions are applied to demonstrate the impact of the 2004 merger regulation, the 2007 guidelines for non-horizontal mergers, and the 2013 merger simplification package on procedural duration. While the 2004 merger regulation has extended the review period, the subsequent guidelines have shortened it. Changes in the probability of prohibition are found to be minor, likely within one percentage point.