Sam has hedged a portfolio of bonds against a small parallel shift in the yield...

When hedging a portfolio of bonds against shifts in the yield curve, using only duration as a measure is effective for small parallel shifts. However, for larger shifts, convexity becomes significant. Convexity accounts for the curvature in the relationship between bond prices and yields, providing a more accurate measure of interest rate risk. To ensure the portfolio is hedged against larger parallel shifts, Sam should take positions that neutralize the portfolio's convexity. This involves adjusting the portfolio in a way that it is less sensitive to changes in interest rates, providing a second-order measure of risk beyond duration.