信用評等調整是否影響企業資本結構的決定？

Does Rating Changes Affect Capital Structure Decision?

本文以1998至2009年間，獲得評等機構給予評等等級的上市、上櫃公司為樣本，探討我國企業資本結構的調整過程，是否納入信用評等為考量。本文納入中華信用評等機構、標準普爾信評機構、惠譽評等機構、台灣惠譽評等機構、穆迪投資服務機構、台灣穆迪投資服務機構，以完整了解各評等機構調整評等等級對我國企業的資本結構之影響。實證結果發現在控制其他可能影響資本結構決定的因素後，評等等級調升使企業的負債比率顯著提升，顯示評等等級調整確實影響企業資本結構的決定。當以淨債務發行增量減去淨股東權益的增加占資產總額的比率衡量資本結構，發現評等等級調整對資本結構沒有顯著的影響，但若將資金籌措的方式細分，發現評等獲得調升的企業，隔年的公司債發行比率顯著上升，顯示我國的企業透過增加發行公司債以回到目標資本結構。

This paper includes the long-term issuer credit ratings issued by 6 rating agencies from 53 firms in Taiwan markets during 1998–2009. We try to investigate the partial adjustment process of capital structure when rating agencies upgrade or downgrade firms' credit ratings. We find firms increase debt ratio when the rating is upgraded but the effect is not significant when the rating is downgraded. Furthermore, firms increase issuing corporate bond when firms' rating is upgraded and the effect is still insignificant when the rating is downgraded.