calculation. I'm sorry you haven't heard about it. It is a widely used measure to evaluate investments with multiple differing cash flows and to generate an overall rate of return based on net present value. As I said in the posts, it has nothing to do with salaried income, but only investments that provide a return. You did not invest anything with your salary and therefore cannot judge your rate of return although it could be used for instance if you were attempting to decide between two different jobs that had differing cash flows to decide which one is the better offer at the present time.
I started to go through the formula, but decided it's not worth it. If you want to learn the formula, it's widely used and you can work your way back through it to come to your own conclusions. All I'll say is that it does work because any number divided by 0 is going to be undefined or some might say infinite. If you don't put any of your own capital at risk your ultimate return is infinite. Evaluate the math yourself.
The irony of your post is noteworthy. Thanks for that...