Basel II regulatory capital formula could imply substantial gaps between the long run PD and the short run historical average. Hence, banks might need to raise their short run historical average of internal PD substantially. Under through-the-cycle rating system, they might have to increase it even more when the economy is in booming period. With more realistic assumption of credit migration, however, we find that gaps are much smaller in many cases. We show, through simulation and a credit card portfolio, that rating pooling can generate substantial variation in BASEL II regulatory capital.
Key Words: BASEL II, probability of default, regulatory capital, pooling, business cycle, rating system
