ambient co2 -- if pushing 50-60grams per sq ft, you are efficiently filling the space. You can only fill an area so much before you increase chances of pathogen, like mildew, creeping in.
optimal environment and genetics - you may push 80/sq ft? 125-133% is a good guess. People measure this fromt he back of the taint sometimes, so it's hard to compare what you read from one garden to the next. some eliminate large proportions of larf, which usualyl reduces overall yield but higher proporiton of better formed nugs... so many variables impact yield that come done to user-preference above and beyond mistakes and better methods. Genetics being the ceiling.. some strains just don't produce donks even if you are optimal in every way. still will be 124-133% more with co2 / environmental controls compared to ambient and loosely controlled environs, but boosted from a lower starting point.
so many variables... hard to say what we do differently is definitively the cause of what we see.... huge sample sizes and understanding a matrix of variables necessary to be certain.