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

Aniss Louchez
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Aniss Louchez: LEM - Lille économie management - UMR 9221 - UA - Université d'Artois - UCL - Université catholique de Lille - Université de Lille - CNRS - Centre National de la Recherche Scientifique

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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)
Date: 2025-03
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Published in Finance Research Letters, 2025, 73, pp.106644. ⟨10.1016/j.frl.2024.106644⟩

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Persistent link: https://EconPapers.repec.org/RePEc:hal:journl:hal-05109800

DOI: 10.1016/j.frl.2024.106644

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