@Fosco
One approach shows that it is increasingly difficult once you get close to 10% improvement to then pass it by much, and also that the significance of passing it by just a little bit is huge because of how hard that is to do.
Like on a guitar, there is a bridge and a nut, and it is very hard for the guitar strings to move any distance at the bridge or at the nut. But in the middle of the fretboard, the guitar strings have the greatest possible freedom of motion.
Meanwhile the 'notes' of different pitch come from logarithmic differential, not linear.
It seems to me that the kaplan-meier style of analysis will impose a mathematical version of the physical guitar kind of constraints on our population (strings)