Pound for Pound (P4P) rankings
From MMA Tycoon Wiki
P4P (pound for pound) rankings are the overall fighter rankings for the game. We take the overall hype rating and rank all the fighters in the game based on that figure, so if your fighter has the highest hype rating, he will be the P4P top ranked fighter in the game.
However, depending on his popularity, he may not be the fighter who draws the highest Event Attendances and Pay Per View, as this is calculated using a combination of both Fighter Hype and Fighter Popularity.