How fake news effects spread in an oligopolistic market — Evidence from the insulin market

Aniss Louchez

Finance Research Letters, 2025, vol. 73, issue C

Abstract: This study analyzes the impact of an event on November 11, 2022, when a fake “certified” Twitter account falsely claimed that Eli Lilly's insulin would be provided for free. We examine spillover effects on competitors within the insulin market oligopoly. Our findings reveal that while competitors experienced short-term impacts, these were weaker and of shorter duration compared to Eli Lilly. Spillovers within the broader pharmaceutical sector were limited to the immediate aftermath. No anticipatory behavior was detected. The effects were confined to American stock exchanges, suggesting an absence of spillovers in European markets.

Keywords: Oligopoly; Insulin market; Eli lilly; Fake news; Spillovers; Event study; Twitter (search for similar items in EconPapers)
JEL-codes: D83 G12 G14 L13 (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:finlet:v:73:y:2025:i:c:s1544612324016738

DOI: 10.1016/j.frl.2024.106644

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