Do Investors Trust in AI Investments of European Companies?

Announcements of emerging technologies often lead to notable stock market reactions, with Artificial Intelligence standing out due to its transformative potential and growing regulatory attention. Yet, most research on investor responses to AI disclosures focuses on U.S. firms, leaving the distinct European context unexplored. Using a short-term event study of 526 AI-related announcements by STOXX Europe 600 firms between 2015 and 2024, we report a significantly negative average stock return of -0.176% within a three-day window. However, announcements detailing specific AI technologies, involving collaborations with AI specialists, or made after the release of ChatGPT are associated with less negative reactions. In contrast, references to EU regulatory frameworks like the AI Act show no significant effect. Our findings confirm generally negative investor reactions to AI announcements but show that in Europe, strategic factors such as announcement specificity, collaborations, and timing also significantly mitigate these effects.