NO.PZ201812310200000201
问题如下：
The most appropriate response to Kowalski’s question regarding credit rating migration is that it has:
选项：
A.a negative impact.
no impact.
a positive impact.
解释：
A is correct. Credit spread migration typically reduces the expected return for two reasons. First, the probabilities for rating changes are not symmetrically distributed around the current rating; they are skewed toward a downgrade rather than an upgrade. Second, the increase in the credit spread is much larger for downgrades than is the decrease in the spread for upgrades.
有negative impace是否是因为成为BB的概率为6.95%，成为A的概率为4.8%
下调的概率大于上升的概率，所以是negative impact。或者说我这个分析跟题目没啥关系？
