所有權結構、董事會組成與買回庫藏股宣告之市場反應

Abstract

本研究旨在探討所有權結構及董事會組成對於買回庫藏股宣告之市場反應的影響。本文是以2000年8月至2009年底宣告買回庫藏股之台灣上市公司為研究對象，僅選取每間公司每年第一次買回庫藏股為樣本，並剔除因目的二(作為股權轉換之用)而買回。篩選後的樣本總計有1133個事件，其中包含420家上市公司。 本研究探討之所有權結構，包括控制股東之現金流量權、控制股東之股份控制權與現金流量權偏離程度、內部人持股比例、外國機構投資人持股比率。董事會組成部分，則包含董事會規模、獨立董事、控制股東占董事席次比例，來探討公司治理之良窳是否影響宣告買回庫藏股之市場反應。 本文之實證結果發現，內部人持股比例、外資機構投資人持股比率均與累積平均異常報酬呈顯著正相關。另外，董事會規模、獨立董事均與累積平均異常報酬呈顯著正相關。而控制股東占董事席次比例與累積平均異常報酬則呈顯著負相關。而關於控制股東之現金流量權、股份控制權與現金流量權間之偏離程度所作之檢定顯示，其與累積平均異常報酬無顯著關係。推究其原因，可能因樣本公司獨立董事及外國機構投資人適時扮演監督角色，使控制股東與少數股東間之代理問題獲得改善，因而降低控制股東因素對庫藏股宣告之市場反應所造成之影響。整體而言，本文的結論支持當公司內部人持股比例較多、外資機構投資人持股比率較高、董事會規模較大、獨立董事較多、控制股東占董事席次比例越低，其宣告買回庫藏股時，可獲得投資人更正面之評價，其買回庫藏股宣告之正向市場反應也較大。

This study investigates the impact of ownership structure and board composition on the market reaction surrounding share repurchase announcement. This thesis examines various ownership structure such as cash flow rights of controlling shareholders, the deviation between cash flow right and control right, shareholdings of insiders, and shareholdings of foreign institutional investors. Moreover, I also use the different measures of board composition, including board size, independent directors, and the percentage of seats held by the controlling shareholders. In sum, this research aims to investigate whether different corporate governance mechanism affects the market reaction surrounding the share repurchase announcement. Empirical results show that firms with higher shareholdings of insiders or higher shareholdings of foreign institutional investors experience a significant positive abnormal return when share repurchase is announced. From board composition perspective, board size and independent directors have positive significant impact on the market return surrounding share repurchase announcement. In addition, the higher percentage of seats held by the controlling shareholders, the less abnormal return surrounding the share repurchase announcement. However, I find the negative market reaction of control—cash flow right deviation is offset by independent directors and foreign institutional investors.