公民營銀行公司治理與放款品質之關聯性研究

Abstract

本研究旨在探討公司治理機制對我國銀行放款品質之影響，特別關注董事會結構與董監事股權特徵在不同所有權類型（公營與民營銀行）下治理效果之差異。本文以2008年至2024年間28家本國銀行為研究樣本，使用月度縱橫資料建立固定效果模型，並納入交乘項與子樣本迴歸分析，以深入檢視治理機制與銀行性質間之交互作用，主要治理變數包括董事會規模、董監事持股比例、外部董事比例與董監事股權質押比例，放款品質則以逾期放款比率（NPL ratio）衡量，控制變數涵蓋經濟成長率、失業率、放款總額與備抵呆帳覆蓋率。 實證結果顯示，公司治理對放款品質具有顯著影響。整體而言，外部董事比例與逾期放款比率呈正向關聯，顯示外部董事可能無法有效發揮實質監督功能，甚至在資訊不對稱與制度落實不足的情況下，對風險控管反而產生不利影響。董事會規模雖在整體樣本中不具顯著性，但在小規模董事會中可明顯降低放款風險，反映出決策效率與責任集中的治理優勢。進一步的交乘分析也顯示，當小董事會結構結合民營銀行制度時，治理效果最為顯著，驗證誘因與組織彈性在治理機制中扮演關鍵角色。董監事持股比例僅在「完全持股與公營銀行」情境下展現統計顯著性，驗證當董監事具備長期財務承擔時，可有效提升放款品質，並降低信貸風險，此結果亦與「利益一致性假說」相符，突顯誘因結構對治理效果之重要性。至於董監事股權質押，在整體模型中不顯著，但在公營銀行中與逾放比呈顯著正向關係，顯示質押行為可能弱化監督誘因並增加風險承擔傾向，特別是在公營比例偏高、外部監督較弱的情境下，此一效果更為明顯。 本研究補足現有文獻對治理效果一致性假設之限制，強調誘因機制與制度背景互動對治理效果之關鍵角色，亦對我國未來銀行治理改革與風險控管政策提供實證依據與建議。

This study investigates the impact of corporate governance mechanisms on loan quality in Taiwan's banking sector, with particular attention to how board structure and insider ownership characteristics interact with ownership type (public vs. private banks). Using monthly panel data from 28 domestic banks during the period 2008 to 2024, this study employs a fixed-effects model and incorporates interaction terms and subsample regressions to explore the joint effects of governance structures and institutional ownership contexts. The key governance variables include board size, insider ownership ratio, proportion of outside directors, and director share pledging ratio. Loan quality is measured by the non-performing loan (NPL) ratio, while control variables include GDP growth, unemployment rate, total loans, and loan loss reserve coverage. Empirical results reveal that corporate governance significantly influences loan quality. Overall, the proportion of outside directors is positively associated with the NPL ratio, suggesting that outside directors may fail to exercise effective oversight and, under conditions of information asymmetry or weak institutional enforcement, may even contribute to increased risk. Board size does not show significant effects in the full sample, but smaller boards are associated with better loan quality, indicating the benefits of streamlined decision-making and concentrated responsibility. Interaction analysis further confirms that the governance effect is strongest when small boards are paired with private bank structures, highlighting the critical role of incentive alignment and organizational flexibility. Insider ownership exhibits significance only under the “full ownership and public bank” condition, supporting the notion that long-term financial commitment by board members enhances governance and mitigates lending risk. This finding aligns with the "alignment of interest hypothesis." Meanwhile, director share pledging is not significant in the overall model but shows a positive and significant relationship with NPLs in public banks, indicating that pledging may weaken governance incentives and elevate risk, especially in state-owned contexts with limited external monitoring. This study contributes to the literature by challenging the assumption of uniform governance effects and underscores the importance of incentive mechanisms and institutional settings. The findings provide empirical implications for future reforms in bank governance and credit risk management in Taiwan.