modified internal rate of return is the least popular of all discounted and non-discounted models. some argue mirr is superior to irr because it allows the manager to adjust the discount rate of intermediate term cash flows to better match a realistic return for the cash flows. samuel c. weaver, director of financial planning and analysis of Hershey foods, commented at the 1988 fma meeting (financial management panel discussion; 1989), reinvestment rate is identical to the discount rate that would have been used for net present value. (mirr) gives the right answer and in such a way that management can understand it as a rate of return.