Yield is a function of energy to the foilage that feeds the flowering buds. The largest bud is usually at the top of the plant since light tends to be placed above a plant. During flowering, if you can distribute energy more evenly among the foiliage, you can increase yield by ~ 1/3 or more. Outdoor growers are reported to attach a string to the top of a plant when flowering begins, and bend the plant in an upside down `U` in order increase light distribution.
Indoor (and outdoor) growing is a really fascinating, information-laden, brain-stimulating endeavour. For what it's worth, marijuana growers often learn and share really awesome info that's applicable to all kinds of grows. Loads of neurons firing over there.
