Jason,
Sure, I'd go with the yard a year, on average, gains due to non-equipment factors. The purification of the golfer-athlete genome. What do you think is the probability of a technology-induced distance jump in the next 10 year; say by 2018? Do you suppose the USGA will be ahead of the curve, if it happens, and regulates it out? Are we at the peak of the distance golden age now?