在過去的群眾募資研究中，學者認為，社群網絡外部性愈強，愈可幫助專案募款表現。然而，從旁觀者效應觀點來看，旁觀的群眾人數愈多，反倒不一定會正面影響群眾募資案之募資表現。本研究認為，當實際的出資贊助者(Backers)數量佔支持者(Supporters)比重低時（即旁觀者效應），反而可能減少專案的募資金額。藉由分析台灣群眾募資平台 flyingV上的5,773個觀察數據，本研究發現，旁觀者效應減低專案的每日募資金額。然而，機構單位提出的群眾募資專案，因其正當性，可降低旁觀者效應對每日募資金額的負面影響。另外，當專案設定的募款天數愈長時，也可以降低旁觀者效應對每日募資金額的負面影響。

From a network externalities perspective, prior studies suggest that social networks can improve fundraising performance on crowdfunding platforms. However, according to the bystander effect in the social psychological literature, the number of project supporters may be negatively associated with fundraising performance. By analyzing 5,773 daily observations from 191 crowdfunding projects on the flyingV platform, we show that the bystander effect harms the daily pledge amount. To mitigate such a negative impact, crowdfunding project creators may signal project legitimacy and use a longer project-funding period to escalate the conversion from bystanders to backers, which in turn enhances the fundraising performance.