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

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  • Louchez, Aniss

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.

Suggested Citation

  • Louchez, Aniss, 2025. "How fake news effects spread in an oligopolistic market — Evidence from the insulin market," Finance Research Letters, Elsevier, vol. 73(C).
    • Handle: RePEc:eee:finlet:v:73:y:2025:i:c:s1544612324016738
    DOI: 10.1016/j.frl.2024.106644
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    More about this item

    Keywords

    Oligopoly; Insulin market; Eli lilly; Fake news; Spillovers; Event study; Twitter;
    All these keywords.

    JEL classification:

    • G14 - Financial Economics - - General Financial Markets - - - Information and Market Efficiency; Event Studies; Insider Trading
    • L13 - Industrial Organization - - Market Structure, Firm Strategy, and Market Performance - - - Oligopoly and Other Imperfect Markets
    • G12 - Financial Economics - - General Financial Markets - - - Asset Pricing; Trading Volume; Bond Interest Rates
    • D83 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Search; Learning; Information and Knowledge; Communication; Belief; Unawareness

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