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.

中文翻译：

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假新闻效应如何在寡头垄断市场中传播 — 来自胰岛素市场的证据


本研究分析了 2022 年 11 月 11 日事件的影响，当时一个虚假的“认证”Twitter 帐户错误地声称礼来的胰岛素将免费提供。我们研究了胰岛素市场寡头垄断中对竞争对手的溢出效应。我们的研究结果表明，虽然竞争对手受到了短期影响，但与礼来相比，这些影响更弱且持续时间更短。更广泛的制药行业的溢出效应仅限于紧随其后的后果。未检测到预期行为。影响仅限于美国证券交易所，这表明欧洲市场没有溢出效应。