本研究旨在說明資本適足率對於銀行業資訊傳遞效果之影響，利用Allen and Gale (2000)模型討論在不完整市場結構下，銀行間因為持有銀行同業存款而形成相連的傳染途徑，進而影響整個系統，本研究擴展Allen and Gale (2000)的模型，加入資本適足率的考量，從而進一步探討透過資本適足要求能否有效提高銀行整體穩定性。

模型假設因為不同區域對於早、晚期消費需求不同，可藉由區域間的資源移轉，來達到最適分配情況。隨著資本適足率的納入，將改變最適分配解，同時分析緩衝(buffer)、擴散效果(spillover effect)及傳染(contagion)的變化。文中傳染定義為擴散效果扣除緩衝力道的淨結果，並說明若有超額流動性消費需求衝擊時，一家銀行的倒閉將如何傳染至整個銀行體系。

此研究發現，在資本適足規定下，若長期資產報酬率越大，會更有機會取得較大的緩衝能力，但將面對較大的擴散效果。關於傳染現象，則是發覺當銀行同業存款越小，在資本適足規定下的傳染機會越低；若長期資產的早期報酬率越大，同樣可降低發生傳染現象機率，即驗證資本適足率對於銀行穩定性的貢獻。

The objective of this study is to testify the effect of capital requirement with regard to information transmission among banks. We develop a model based on Allen and Gale (2000) to discuss that under incomplete market structure, contagion channel is built because of interbank deposits market. We also expand Allen and Gale’s model by putting new parameter, capital requirement, into this model to analyze the impact of capital requirement with respect to stability in banking system.

Due to different liquidity demands at each date in different regions, banks can exchange resources in the system to reach the first-best allocation. With capital requirement, the first-best allocation varies and so does buffer, spillover effect and contagion. In this article, contagion is defined as the net result of spillover effect minus buffer. Besides, we explain how the bankruptcy in one region evolves into the bankruptcy in the whole system under excess demand for liquidity.

We find out that with capital requirement, if return of long-term asset at final date is higher, there will be more chances to have more buffers but larger spillover effect. As for contagion, it shows that with lower interbank deposits or higher return of long-term asset at early date, the possibility of contagion will be reduced. As a result, we can conclude that capital requirement really improves the stability in banking system.

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