2005年-世界发展银行全球_Credit_Risk_Measurement_Under_Basel_II___An_Overview_and_Implementation_Issues_for_Developing_Countries_33页_1mb

Credit Risk Measurement Under Basel II: An Overview and Implementation Issues for Developing Countries

Core Content

This paper provides an overview of the changes in credit risk measurement under Basel II and discusses the challenges of implementing these rules in developing countries. It emphasizes that Basel II is not a revolutionary change but a codification of existing good practices in risk measurement, aiming to align regulatory capital requirements more closely with banks' actual risk profiles. However, the paper highlights that the implementation of Basel II in developing countries is hindered by weak financial infrastructure.

Main Objectives

• To describe the theoretical and empirical developments in credit risk measurement that influenced Basel II
• To summarize the treatment of credit risk under Pillar 1 of Basel II
• To identify implementation issues and policy implications for developing countries

Key Concepts in Credit Risk Measurement

1. Credit Risk Definition

Credit risk traditionally refers to the risk of loss due to a borrower or counterparty's failure to repay the loan. A more comprehensive view includes value risk, which arises from a borrower's credit rating migration without defaulting.

2. Expected Loss (EL)

EL is calculated as:

$$
\mathrm{EL} = \mathrm{PD} \times \mathrm{EAD} \times \mathrm{LGD}
$$

Where:

• PD (Probability of Default): Likelihood of default over a specified time horizon
• EAD (Exposure at Default): Outstanding amount at the time of default
• LGD (Loss Given Default): Percentage of EAD lost in the event of default

EL is used to estimate the cost of doing business and should be incorporated into loan pricing and provisioning.

3. Unexpected Loss (UL)

UL represents the volatility in actual loss levels and is used to determine the capital required to cushion against potential losses. It is calculated as the standard deviation of EL:

$$
\mathrm{UL} = \boldsymbol{s}(\mathrm{EL}) = \boldsymbol{s}(\mathrm{PD} \times \mathrm{EAD} \times \mathrm{LGD})
$$

For a single loan, UL is often simplified to:

$$
\mathrm{UL} = \sqrt{\mathrm{EL}(\mathrm{EAD} \times \mathrm{LGD} - \mathrm{EL})}
$$

4. Portfolio-Level Unexpected Loss

UL at the portfolio level is not simply the sum of individual ULs due to the correlation between defaults. The formula for portfolio UL is:

$$
\mathrm{UL}{P}^2 = \sum{i=1}^{N} \sum_{j=1}^{N} \boldsymbol{r}_{i,j} \mathrm{UL}_i \mathrm{UL}_j
$$

Where:

• $\boldsymbol{r}_{i,j}$: Pair-wise correlation between loans i and j
• $\mathrm{UL}_{P}$: Portfolio-level Unexpected Loss

This highlights the importance of diversification and correlation analysis in credit risk management.

Basel II Framework

Basel II consists of three Pillars:

• Pillar 1: Minimum capital requirements for credit and operational risk
• Pillar 2: Supervisory oversight and risk management practices
• Pillar 3: Public disclosure of risk and capital information to encourage market discipline

The framework aims to:

• Improve risk sensitivity in capital requirements
• Introduce operational risk capital charges
• Maintain the overall level of capital requirements but encourage the use of more advanced risk-sensitive methods

Implementation Issues for Developing Countries

Despite the improvements in Basel II, its implementation in developing countries is challenging due to:

• Weak financial infrastructure: Lack of robust accounting, legal, and data systems
• Limited historical data: Essential for empirical models of PD and LGD
• Inadequate risk management capabilities: Many banks lack the expertise to develop sophisticated internal models
• Limited market depth: Market-based approaches for PD estimation are not feasible in many developing markets
• Sovereign risk mispricing: Basel I's treatment of sovereign risk led to mispricing and lack of diversification, which Basel II does not fully resolve

These issues suggest that developing countries need to invest in financial infrastructure, data collection, and risk management capabilities before implementing Basel II effectively.

Policy Implications

• Infrastructure development is a priority to support the implementation of Basel II
• Enhanced risk measurement and management practices are needed to ensure that capital requirements reflect actual risk
• Public disclosure and market discipline should be encouraged to improve transparency and accountability
• Sovereign risk should be addressed through better risk assessment and diversification strategies

Conclusion

While Basel II represents a significant step forward in aligning regulatory capital requirements with actual risk, its implementation in developing countries is constrained by existing weaknesses in financial systems. Therefore, before adopting Basel II, developing countries should focus on strengthening their financial infrastructure and risk management frameworks.