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This page lists the project publications as well as selected other publications making use of the EUPLEX dataset.

Project publications

Hurka, S., Haag, M. and Kaplaner, C. (2022) Proposal complexity and report allocation in the European Parliament. European Union Politics.
doi: 10.1177/14651165221144888

Abstract: Experience and loyalty have been identified as major explanations for why Members of the European Parliament (MEPs) are selected as committee rapporteurs in the European Parliament. Yet, existing research implicitly assumes that these explanations operate in isolation of what the report is about. In this article, we hypothesize that the effects of experience and loyalty on MEPs’ chances to become rapporteurs should be conditioned by the complexity of the Commission's legislative proposal. We show that party group coordinators indeed distribute the most complex legislative tasks to highly experienced MEPs but cannot confirm such a conditional relationship for the effect of loyalty. Our study contributes to the literature on the legislative organization in the European Parliament by highlighting the role of proposal complexity for the report allocation process.

Hurka, S. (2022) The institutional and political roots of complex policies: Evidence from the European Union. European Journal of Political Research.
doi: 10.1111/1475-6765.12555ECPR The Loop article

Abstract: The complexity of public policies has repeatedly been identified as a key challenge for modern democracies. Yet, we know only very little about the origins of this complexity. Controlling for functional and legal explanations, this article investigates whether complex policies have distinct institutional and political origins. The study builds on the assumption that complex policies are communicated in more complex language and uses textual data from 1771 legislative proposals issued by the European Commission since 1994 to demonstrate that the complexity of public policies is strongly tied to institutional and political costs of policy formulation. Collegial cabinets formulate more complex policies whenever they face more inclusive decision-making processes and struggle with higher internal preference bias and heterogeneity. The implications of these findings reach far beyond the political system of the European Union and highlight that to a considerable degree, complex policies are the price of inclusive democratic decision making.

Hurka, S., Haag, M. and Kaplaner, C. (2022) Policy complexity in the European Union, 1993-today: introducing the EUPLEX dataset. Journal of European Public Policy, 29(9), 1512-1527.
doi: 10.1080/13501763.2021.1938174 PDFReplication material (.zip) Dataset

Abstract: Despite its importance for the sustainability of democratic governance, policy complexity is still an understudied phenomenon. What makes policies complex? Why are some policies more complex than others? And what are the consequences of this complexity for the political, economic and societal level? These questions still lack answers, which is both due to a lack of conceptual clarity and a lack of suitable data. In order to tackle these challenges, we introduce the EUPLEX dataset, comprising information on the complexity of more than 6,000 policy proposals adopted by the European Commission between 1993 and today. Relying on automated methods of data collection and natural language processing, EUPLEX allows us to compare the complexity of Commission proposals over time, across policy domains, and institutional and political configurations. The dataset will be updated continuously in the future as new policy proposals become available and is available free-of-charge to the research community.

Adam, C., Hurka, S., Knill, C. and Steinebach, Y. (2021) On democratic intelligence and failure: The vice and virtue of incrementalism under political fragmentation and policy accumulation. Governance.
doi: 10.1111/gove.12595

Abstract: The vice and virtue of incrementalism have been the subject of a long‐standing academic debate. This debate, however, lacks a dynamic perspective that analyzes how the transformation of politics—mainly in the form of increasing levels of political fragmentation within decision‐making arenas and increasing complexity of policy‐mixes—affects the role of incrementalism. We argue that both of these trends make the virtues of incrementalism politically even more valuable than they have always been. At the same time, this proliferation of incrementalism comes at the costs of overlooked second‐order effects. Since the empirical reality of incrementalism is primarily one that results in incremental policy accumulation, it continuously adds implementation burdens, enhances the demandingness of substantive policy debate, and makes effective science communication more difficult. Thereby, accumulative incrementalism becomes one source of pressure on three cornerstones of legitimate governance: effective policy implementation, sophisticated policy debate, and evidence‐based policymaking.

Hurka, S. and Steinebach, Y. (2020) Legal Instrument Choice in the European Union. Journal of Common Market Studies.
doi: 10.1111/jcms.13068 PDF

Abstract: Regulations and directives are the central legal instruments used by the EU. In some instances, the Commission is not legally required to choose a specific legal instrument, but can make this decision autonomously. However, we know surprisingly little about the factors that influence this decision. Based on an original dataset of all directives and regulations proposed by the European Commission in ordinary legislative procedures between 2009 and 2018, we find that the choice of a legal instrument is strongly determined by prior policy decisions and varies systematically across policy areas depending on the extent to which they have traditionally been addressed under the co‐decision procedure. In addition, we find that the Commission's use of regulations increases under conditions of increased euroscepticism, indicating that instead of granting dissenting member states more room to manoeuvre, the Commission prefers to keep them on a short leash.

Hurka, S. and Haag, M. (2020) Policy complexity and legislative duration in the European Union. European Union Politics, 21(1), 87–108.
doi: 10.1177/1465116519859431 PDFReplication material (.zip) LSE EUROPP article

Abstract: This article investigates the impact of policy complexity on the duration of legislative negotiations in the European Union employing survival analysis. We conceptualize policy complexity as a three-dimensional construct encompassing structural, linguistic and relational components. Building on this conceptual framework, we measure the complexity of 889 Commission proposals published under the ordinary legislative procedure between 2009 and 2018. Controlling for institutional and political drivers of legislative duration identified by previous studies, we show that different types of policy complexity influence the duration of the decision-making process in the European Union to varying degrees, at different points in time and partially in unexpected ways. On a general level, our study highlights that developing a better understanding of the origins and consequences of policy complexity in the European Union is a key task for scholars of European integration.

Working papers

Haag, M., Hurka, S. and Kaplaner, C. (2023) Policy complexity, transposition delay and implementation performance in the European Union. Paper presented at the 2023 EPSA conference, Glasgow, 22-24 June 2023.


How does the complexity of EU directives affect their transposition and implementation at the national level? The answers of the EU implementation literature to this question are quite mixed. In this study, we argue that those inconclusive findings might be due the fact that the complexity of EU directives has never been measured properly. Instead, the existing literature typically uses the number of recitals preceding the enacting terms of the directive as a proxy for the directive's complexity. However, this measure has two important limitations that question its suitability for implementation research: First, recitals have no autonomous legal effects and second, the ways in which recitals have been used by the legal drafters of the EU has been varying tremendously over time. We therefore suggest that in order to measure the 'burden of implementation' on member states induced by the complexity of EU policy, the actual legal provisions of a given directive should be taken into account. We propose to measure policy complexity on the basis of the enacting terms of the directives and argue that complexity can feed from different sources (structural, linguistic and relational), which have varying effects on member state compliance. Empirically, we evaluate the extent to which those different types of policy complexity are associated with transposition delays and infringement proceedings, following the adoption of roughly 1,000 EU directives between 1993 and 2021. The analysis yields new insights into how complexity-induced costs of compliance affect the performance of EU member states at the implementation stage.

Kaplaner, C., Haag, M. and Hurka, S. (2021) Proposing an index of policy complexity. Paper presented at the 5th International Conference on Public Policy (ICPP), Virtual, 5-9 July 2021.


Researchers and practitioners alike have long been aware of the importance of policy complexity in the different steps of the policy-making cycle – be it the need for consultation (Van Ballaert, 2017), the duration of legislative negotiations (Hurka & Haag, 2019), the delegation of rule-making authority (Senninger, 2020), or the burden of implementation and application (Limberg et al., 2020). One consistent observation across these studies is that complexity often raises the transaction costs of engaging with a policy. This awareness has resulted in multiple conceptualizations and operationalizations to capture complexity in political and legal science. Yet, existing approaches often only capture certain aspects of policy complexity and are commonly specific to a given research context. Following previous work, we conceptualize policy complexity as a combination of three components: (1) the structural, (2) linguistic, and (3) relational complexity of a legal text. We generate sub-indices for each component by combining different methods from the realm of quantitative text-analysis and natural language processing. In a second step, we aggregate the sub-indices into an index of policy complexity, accounting for the possibility that the transaction costs generated by different types of policy complexity might vary depending on the capacities of different types of end-users (public, decision-makers, implementers). Along these lines, we present a research design for the creation of a flexible weighting scheme to make the index adaptable to different research contexts. We validate the index against suspected drivers of complexity such as the width of the issue area and the underlying legal basis. The contribution of this work is two-fold. First, we provide an index of policy complexity in the EU that allows researchers to use aggregation weights suitable to their specific research question. Second, we provide a baseline aggregation process that is adaptable to legislative text data from different legal systems.

Hurka, S., Haag, M. and Kaplaner, C. (2021) How proposal complexity conditions report allocation in the European Parliament. Paper presented at the 2nd Virtual Conference of the European Political Science Association (EPSA), 24-25 June 2021.

Haag, M., Kaplaner, C. and Hurka, S. (2021) From bill to law: how the complexity of policy proposals evolves over the European Union’s legislative process. Paper presented at the 2nd Virtual Conference of the European Political Science Association (EPSA), 24-25 June 2021.


The content of policy proposals changes to varying extents over the course of the legislative process. In some instances, the text introduced by the agenda setter is almost left untouched by the decision-makers; in other cases, the final act hardly resembles the initial proposal. Yet, despite its strong relevance for the field of legislative politics, the question of how this variance can be explained is still unresolved. In this paper, we contribute to a better understanding of how legislative proposals evolve before they become law by focusing on changes in their complexity. Specifically, we investigate how the complexity of policy proposals adopted by the European Commission between 1994 and 2021 changed during their respective legislative negotiations. We employ a text-as-data approach to measure several indicators of policy complexity, track the changes of these indicators as the Commission proposals move through the EU’s legislative process and analyze the degree to which institutional and political factors help to explain the existing variance in complexity change. In particular, we put our theoretical focus on the inclusiveness of the decision-making process and on the preference heterogeneity of the involved political actors. The analysis thus adopts an innovative perspective on the analysis of legislative negotiations and sheds new light on the crucial question of how legislative institutions and political actors jointly shape the complexity of policy output.

Hurka, S. (2021) The political and institutional roots of complex policies: evidence from the European Union. Paper presented at the 10th Conference of the ECPR Standing Group on the European Union (SGEU), Virtual, 10-12 June 2021.

Hurka, S. and Haag, M. (2020) The evolution of policy complexity in the European Union. Paper presented at EPSA 10th Annual (virtual) Conference.
Presentation slides


Although policy complexity has been identified as one of the major challenges for the European Union (EU) both by practitioners and EU scholars, the complexity of EU legislation is rarely measured and studied systematically. In this paper, we trace the complexity of policy proposals published by the European Commission under the co-decision and the consultation procedures since the Maastricht Treaty. We investigate how policy complexity has evolved over time and assess the extent to which this complexity is affected by the increasing involvement of the European Parliament in the decision-making process and the legal instrument used by the Commission. We analyze several indicators of policy complexity, covering structural, linguistic and legal aspects. The analysis is currently based on more than 4,000 legislative proposals. We find that (a) policy complexity has clearly been on the rise in the EU while the growth rate has slowed down more recently, that (b) the Commission adopts significantly more complex policy proposals under co-decision than under consultation and that (c) the conventional wisdom that regulations carry more complex policy content than directives should be re-considered. The paper thus contributes to a better understanding of how political institutions shape the complexity of policy content in the EU.

Hurka, S., Haag, M. and Kaplaner, C. (2019) Committee types, policy complexity and legislative efficiency. Paper presented at the 9th Annual Conference of the European Political Science Association (EPSA), Belfast, Northern Ireland, 20-22 June 2019.