问题如下：
Compared with the identical option-free bond, the existence of the embedded call option in the callable bond:
选项：
A.decrease the effective duration of the bond.
B.increase the effective duration of the bond.
C.does not affect the effective duration of the bond.
解释：
A is correct.
Bond with embedded option tends to have lower duration.
If the credit risk doesn't change, the existence of a call option gives the issuer a chance to buy back the bond before its maturity, so the sensitivity of the bond price to changes in the benchmark yield will be reduced, so that the effective duration decreases.
老师，这题可以在解释下嘛？谢谢~
我的理解是，因为含权债券会是duration降低，那相较于不含权债券不是应该increase affect 吗？为什么反而选择decrease affect?
