Question: What is the ranking system used in combat sports, including boxing and mixed martial arts, of who the better fighters are relative to their weight, by which measure the Polish mixed martial artist Joanna Jędrzejczyk is rated the number 1 female MMA fighter in the world?
Sentence (from "Pound for pound"): As these fighters do not compete directly, judging the best fighter pound for pound is subjective, and ratings vary.
Relevant evidence: No