本文分別以配對公司市價淨值法(PBR_M)與歷史股價市價淨值法(PBR_H)作為股價高估指標,討論股價高估與投資人的交易行為如何影響SEO長短期異常現象。實證結果顯示:現增期間股價的高估,會加劇短期的宣告負向效果、使折價幅度更大、降低上市後的初始報酬。然而,兩種股價高估對長期績效卻有不同的影響:配對公司法的股價高估對長期績效有正向影響;歷史股價法的股價高估卻造成SEO長期績效不彰。本文因而推論:配對公司法的股價高估(高PBR_M)比較傾向如Hovakimian(2006)所言的”高成長、高潛力公司”。反之,歷史股價法的下的高市價淨值比,則純屬短期股價高估。最後,由於在SEO期間,內部投資人會買進高PBR_M、賣出高PBR_H,外部投資人則是賣出高PBR_M,本文推論:內部投資人的選股能力較外部投資人為佳。
Adapting comparable firm's P/B ratio (PBR_M) and historical P/B ratio (PBR_H), we explore how overvaluation and investors' trading affect SEO anomalies. Our empirical results indicate that overvaluation negatively affects announcement effect, initial returns, and positively affects discounting. Moreover, as PBR_M (PBR_H) has a positive (negative) impact on long-term performance, we conclude that the company with high PBR_M is high potential while the company with high PBR_H is overvaluation. Finally, we infer that inside investors have better stock selection ability for they buy-in high potential SEOs and sell-out overvaluation SEOs.