本篇論文試圖從比較強勢銀行與弱勢銀行等雙寡頭假設銀行在面對政府提供弱銀行救助的情況下違約風險的變動之論點，應用Hoshi and Kashyap (2010)針對政府介入銀行市場並且提供救助有利於弱銀行的觀點以及Merton (1973、1974)分別針對弱銀行與強銀行在面對政府救助的情況下的股權變動的觀點，導入具有能夠評估市場價值(market value)之Black and Scholes (1973)選擇評價模式，利於比較靜態分析來解釋強銀行與弱銀行在面對政府藉由採購不良貸款和直接注資等措施救助弱銀行下，銀行利差、銀行體系穩定性的變動，將如何影響強銀行與弱銀行的違約風險的變動。
利用上述研究方法證明當政府救助增加時，直接降低了受政府協助的弱銀行的違約風險，卻也間接地提升了強銀行的違約風險，另外，由於政府的介入使得強銀行違約風險上升程度所帶來的間接效果不足以抵銷弱銀行違約風險降低的直接效果，因此，政府的救助將有效降低銀行的違約風險，同時有利於銀行體系的穩定。 A duopolistic loan market includes a strong bank without the problem of early closure that opts out of government bailouts and a weak bank with the problem that participates in the bailout programs of distressed loan purchases and direct equity injections. A direct implication of our framework is that the strong bank’s equity will be priced as a standard call option and the weak bank’s equity will be priced as a down-and-out call option. We find that an increase in either the bailout directly decreases the weak bank’s default risk, but indirectly increases the strong bank’s default risk. Accordingly, either the bailout contributes banking stability since the indirect positive effect insufficiently offsets the direct negative effect to give an overall negative response of default risks to an increase in either the bailout. Higher competition by shifting to quasi-competition from collusion increases banking stability under either the bailout.
