Don't get too hung up on yield, but a good analogy I use is to imagine the five main factors in growing, namely, Light, Soil, Water, Feeding, and Ventilation to be a chain,----the weakest link in this chain is how high/low your yield might be. Genetic type is very important too---so--If your strain is agreeable to providing a decent yield in the first place, then your yield will be as much as the weakest link in your chain, so say you have top nothch lights, soil, nutes and good PH'd water, but ventilation isn't the best, then improving ventilation is your key to a better yield, keep improving the weakest link and your grow(s) will also improve.