Sorry, I thought it was obvious, but apparently it escapes you so let me explain. What it's based on would be the information and methods used to arrive at the conclusion that 1500 ft-lbs is a good benchmark for the "minimum kinetic energy" for killing elk.
In other words, who came up with the 1500 ft-lb benchmark, and how did he get there? What information did he evaluate and how did he evaluate it in order to conclude that 1500 is the right number? Why not 1250 ft-lbs, or 2,000, I've seen 2,000 thrown around too?
So, what is the magical 1500 ft-lbs based on ?
And as far as your comment below, it's telling that you don't believe first-hand experience shooting elk with a bullet that delivers less than 1500 ft-lbs is a good basis to form an opinion. Obviously because you've never done it.
Actually by now I doubt anything you proclaim
Not sure why you think the 1500 fp is a magical number you keep saying that, yet I never did, it is simply a Rule of Thumb an "Axiom" to put people in the correct arena of power for an Elk hunt
I have seen 2000 and 1000 at 100 yards etc etc these are all just recommendations, again What I said in the OP along with examples of what comes close
This seems to be offensive to you to have a good basis of where to start when looking for an Elk round, you don't seem to understand it eliminates very few rounds and gives a new hunter an idea of a starting point..You simply want to pigeonhole the 1500 fp and I think it is more ignorance and ego now that you have back yourself into a corner
Deal with it
Also this shows Ego nothing more it isn't something to brag about
"it's telling that you don't believe first-hand experience shooting elk with a bullet that delivers less than 1500 ft-lbs is a good basis to form an opinion. Obviously because you've never done it." 
