食安事件對食品業股價之研究

Abstract

本研究藉由四個臺灣近年來造成社會恐慌的食安事件，觀察在事件日當天事件主要公司是否存在負異常報酬，以探討會計資訊內涵假說；並研究投資人之從眾行為。本研究選取塑化劑事件、胖達人事件、大統沙拉油事件、頂新黑心油事件，利用事件研究法，以四個事件發生點做為事件日。 本研究發現，在塑化劑事件日下，統一公司存在負異常報酬。頂新黑心油事件日下，味全公司和整個食品業有負異常報酬。大統沙拉油事件日下，對手公司及食品類股具有正向異常報酬。胖達人事件日下，食品股沒有顯著異常報酬。研究結果表示負面食安事件發生時，投資人預期負面消息將導致該公司淨利受到傷害，使得事件發生的公司，產生負異常報酬。我們也發現，臺灣的股市，會因為負面的食安消息，使得投資人發生從眾行為，進而影響到整個食品業的大盤，連帶產生負異常報酬。

This paper has chosen four high profile Taiwanese food safety scandals occurred in the recent years, to understand whether these events generate negative excess returns, and to prove the theory of information content. This paper collects stock prices of food industry, to research the herding effect of the investors. This paper employs four events: the plasticizer event, the Top-Pot bakery event, the Datong oil event, and the Ting-Hsin oil event. The results exhibit the significantly negative excess returns on the Uni-President corporation during the period of the plasticizer event, the significantly negative excess returns on both Wei-Chuan and food industry stocks during the period of the Ting-Hsin oil event, the significantly positive excess returns on both rival companys of Datong company and food industry stocks during the period of the Datong oil event, and the insignificantly negative excess returns on food industry stocks during the period of the Top-Pot bakery event. The conclusion shows when the food safety event happens, the investors expect food safety event will make the company’s profits decline so as to make the company has significantly negative excess returns. The conclusion also shows herding effects of the investors, when the food safety event happens, that will make the prominent negative excess returns on the entire food industry stocks.