A portfolio manager purchases a floating rate mortgage backed security that would currently provide a 4% yield to the company. Since mortgage rates have been fluctuating significantly over the past month, the manager is thinking about entering into an interest rate swap to hedge against the rate movements. Although the manager would remove most of the price sensitivity of the asset by executing the swap, it would also lower the total yield on the investment due to swap costs. What objective in the company investment policy is guiding the portfolio manager’s decision?