We could always start with 100% and see how it goes. I suspect this upper bound method was applied by more than one writer.
Never mind the quibbles, it's good to see this one back. As the footnote says, there's genius in it.
Especially as the two supporting points (a: unpleasant letdowns; b: frequent bothering ``at the wrong moment'') are quite subjective.
To quote the venerable fortune(6):
Man is the highest animal. Man does the classifying.