Adjusting Dollar Duration - Fixed Inc PM I

Reading # 21: (LOS 21.h)

In the Schweser Example, an adjustment of Dollar Duration (DD) was shown for an overall Increase of Interest Rates. In this case, I have noticed that Duration of each of the four bonds Increased as well and their market values have Decreased.

My question is : what happens to Duration , and Adjustment of DD if interest rates Decrease after one year.

Thank you in advance.