Colum

This really tripped me up on the CFAI 2011 Mock (spoiler alert)

Question 33, regarding tracking error: I don't understand- why is there more tracking error from the different contributions of spread duration? Corporates have a different spread duration in the portfolio from the index. But Treasuries have a larger difference in the actual duration. Why isn't this difference in duration more important than the difference in spread duration? Thanks for any illumination on this!