This study tests the information leakage hypothesis prior to the public announcement of firms switching between the Alternative Investment Market (AIM) and the Main Market (MM) in the UK. We find significant abnormal stock returns 60 trading days prior to the announcement of these switches. The results are robust after controlling for switching anticipation, rumors, other major corporate announcements, and firm performance one year prior to the switch. We also show that having a reputable Nominated Adviser (Nomad) significantly moderates the abnormal stock returns prior to market switches. However, this effect does not hold when Nomads also act as brokers in firms that switch markets. Overall, these findings provide novel evidence about abnormal stock returns prior to the announcement of market switches in the UK and the role of Nomads. As such, we shed light on the significance and the limits of decentralized regulation on informed trading activity.

中文翻译：

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市场转换前的信息泄露以及指定顾问的重要性


本研究在英国另类投资市场 (AIM) 和主要市场 (MM) 之间切换的公司公开宣布之前测试了信息泄漏假设。我们发现在宣布这些转换之前 60 个交易日，股票回报出现显着异常。在控制了转换预期、谣言、其他主要公司公告以及转换前一年的公司业绩后，结果非常强劲。我们还表明，拥有一位信誉良好的指定顾问（Nomad）可以显着缓解市场转换之前的异常股票回报。然而，当游牧民族同时充当转换市场的公司的经纪人时，这种效应就不成立。总体而言，这些发现为英国宣布市场转换之前的异常股票回报以及游牧民族的作用提供了新的证据。因此，我们阐明了对知情交易活动进行分散监管的重要性和局限性。