When managing a bond portfolio one of the key ways to beat a benchmark is to predict where a yield curve might be moving towards and to position the portfolio to take advantage of those anticipated movements in the yield curve. There are many ways in which the yield curve can move but the main way that yield curves change is by shifts in the yield curve, which is a term used to describe a parallel movement of interest rates across the entire length of the yield curve, which could either be interest rates increasing getting an upward shift in the yield curve or interest rates decreasing leading to a downward shift in the yield curve. If a portfolio manager is able to predict that movement in the yield curve and a portfolio manager is able to position their portfolio to take advantage of these changes. Then that portfolio manager may be able to beat their Benchmark and the main metric used by portfolio managers to position their portfolios to take advantage of these parallel shifts in the yield curve is duration because duration just uses one measure the yield and if we're saying that the yield of a portfolio changes where effectively saying that all of the yields on all of the bonds within the portfolio Changed by the same amount so duration can be a good metric to identify the impact on a portfolio from a parallel yield curve shift.