我想请问一下:算出来的money-weighted rate of return 和 time-weighted rate of return 有什么作用?怎么用来衡量portfolio performance?象IRR rule就是accept projects or investments for which the IRR is greater than the oppoortunity cost of capital,但是算出来的money-weighted rate of return 和 time-weighted rate of return是越大越好还是越小越好,还是要和正式的discout rate 做比较?