永續發展公司債發行動機

本研究主要欲驗證我國企業發行永續發展公司債券的動機，究竟是基於傳遞企業投入永續行為正向的訊號內容，抑或僅是企業的漂綠行為，又或是取得低資金成本的發行動機。本研究利用事件研究法及差異中之差異(DiD)方法，透過發行宣告股票市場的反映，以及發行後企業ESG績效變化及殖利率的觀察，以探討企業發行永續發展公司債之動機。實證結果顯示，企業永續發展公司債券的發行具有正向的訊息內涵，且股市會於宣告前提前反應；此外，相較於發行一般公司債的配對企業，發行永續發展公司債企業的ESG績效無論於發行前或發行後1-2年皆有顯著的提升，符合訊號理論所稱，企業發行動機主要可傳遞出企業致力於永續發展之論述，而非漂綠；其中，對債信評等較佳的公司債發行企業尤為顯著。最後，永續發展公司債的票面利率與殖利率，皆顯著高於非永續發展公司債，投資人存在永續溢酬，代表企業發行永續發展債券並非基於取得較低資金成本的融資來源，與資金成本理論論述不符。

This study aims to verify whether the motivation of Taiwanese companies issuing sustainable development corporate bonds is based on signaling their positive commitment to sustainability, or is it just greenwashing, or obtaining lower debt costs. Using event study methodology and the difference-in-differences (DiD) approach, the research examines stock market reactions to issuance announcements, as well as changes in ESG performance post-issuance and yield rates to explore these motivations. Empirical results indicate that issuing sustainability bonds carries positive signaling content, with the stock market reacting in advance of the announcement. Moreover, compared to matched companies issuing regular corporate bonds, those issuing sustainability bonds show significant improvements in ESG performance both before and 1-2 years after issuance. This aligns with signaling theory, suggesting that the primary motivation for issuance is to convey the company's commitment to sustainability rather than greenwashing. This effect is particularly notable among companies with higher credit ratings. Finally, the coupon rates and yield rate of sustainable bonds are significantly higher than those of non-sustainable bonds, indicating the presence of a sustainability premium among investors. This finding suggests that the motivation behind issuing sustainable bonds is not to secure lower-cost funding, contradicting the cost of capital theory.