  A lack of political legitimacy undermines the ability of the European Union
to resolve major crises and threatens the stability of the system as a whole.
By integrating digital data into political processes, the EU seeks to base
decision-making increasingly on sound empirical evidence. In particular,
artificial intelligence systems have the potential to increase political
legitimacy by identifying pressing societal issues, forecasting potential
policy outcomes, informing the policy process, and evaluating policy
effectiveness. This paper investigates how citizens perceptions of EU input,
throughput, and output legitimacy are influenced by three distinct
decision-making arrangements. First, independent human decision-making, HDM,
Second, independent algorithmic decision-making, ADM, and, third, hybrid
decision-making by EU politicians and AI-based systems together. The results of
a pre-registered online experiment with 572 respondents suggest that existing
EU decision-making arrangements are still perceived as the most democratic -
input legitimacy. However, regarding the decision-making process itself -
throughput legitimacy - and its policy outcomes - output legitimacy, no
difference was observed between the status quo and hybrid decision-making
involving both ADM and democratically elected EU institutions. Where ADM
systems are the sole decision-maker, respondents tend to perceive these as
illegitimate. The paper discusses the implications of these findings for EU
legitimacy and data-driven policy-making.
