Why you must measure your investing performance and express it in numbers?
XIRR, CAGR, ROC, Win/Loss, Win $/Loss $, etc
Number, Number, Number!
measure what you are speaking about, and express it in numbers, you know
something about it; but when you cannot measure it, when you cannot express it
in numbers, your knowledge of it is of a meager and unsatisfactory kind; it may
be the beginning of knowledge, but you have scarcely, in your thoughts,
advanced it to the stage of science.
Sir William Thompson, Lord Kelvin (1824-1907)