So we use duration and convexity to calculate the change in price for a bond with the following formula: Chg in P = Dur * (Chg in Y) * P + Conv * (Chg in Y)^2 * 0.5 * P I thought that key rate durations were a tool to manage yield curve more effectively and therefore be able to estimate a change in price more accurately. I used the following formula to calculate this change in price with KR durs: Chg in P = [ D1, D2, D3, D4 ] * [ Chg in Y1, Chg in Y2, Chg in Y3, Chg in Y4 ] * P 1:4 being the key rate term. I noticed that when we have parallel shifts we obtain the same price aproximation as with total duration, and that the price approximation is worse when I use key rate durations. Aren't we supposed to obtain a better approximation? Thanks!