The origins of EU legislation: agenda-setting, intra-institutional decision-making or interinstitutional negotiations? Thomas Laloux a and Tom Delreux b a Fonds de la Recherche Scientifique-FNRS - UCLouvain, Institut de sciences politiques Louvain-Europe, Louvain-la-Neuve, Belgium; b UCLouvain, Institut de sciences politiques Louvain-Europe, Louvain-la-Neuve, Belgium ABSTRACT This article traces the origins of European legislation during the legislative policy-making process. It identifies three phases where parts of the text of legislative acts can be developed: (1) agenda-setting; (2) intra-institutional decision-making and (3) interinstitutional negotiations, depending on whether the content of the legislation originates respectively in the Commission pro- posal, the co-legislators’ positions or trilogue negotiations. Using a newly developed text-mining technique which computes in which phase each word of a legislative act originally appears, the article examines the relative import- ance of each phase and explores how it is affected by interinstitutional con- flict. Applying this method to 219 legislative acts adopted between 2012 and 2018, it finds that most EU legislation originates in the agenda-setting phase, and that the new content developed during trilogue negotiations is limited. However, the importance of the agenda-setting phase decreases in cases with high levels of interinstitutional conflict. KEYWORDS European Union; interinstitutional negotiations; ordinary legislative procedure; text- mining; trilogues Introduction This article traces the origins of European legislation during the legislative policy-making process. Legislative acts in the European Union (EU) are adopted by the co-legislators, i.e. the Council and the European Parliament (EP), who can amend the proposal issued by the Commission. Legislative acts are thus compromises between the text initially proposed by the agenda-setting Commission; amendments that are the result of intra-institutional decision-making in the Council and the EP; and CONTACT Thomas Laloux thomas.g.laloux@uclouvain.be Supplemental data for this article can be accessed online at: https://doi.org/10.1080/01402382. 2020.1836861. ß 2020 Informa UK Limited, trading as Taylor & Francis Group WEST EUROPEAN POLITICS 2021, VOL. 44, NO. 7, 1555–1576 https://doi.org/10.1080/01402382.2020.1836861