Convexity is a measure of the amount of “whip” in the bond’s price yield curve and is so named because of the convex shape of the curve. Because of the shape of the price yield curve, for a given change in yield down or up, the gain in price for a drop in yield will be greater than the fall in price due to an equal rise in yields. This slight “upside capture, downside protection” is what convexity accounts for.
Convexity is important as it illustrates the impact that changes in yields have on the duration of the bond. As yields approach zero the duration impact of a movement in yields is accentuated. Large moves in the yield curve can have large nonlinear effects on duration, making convexity an important consideration during volatile markets.
Convexity Price vs Yield Graph