So often, we hear of numbers such as 99% or 99.9% of germs killed; or something being 90 or 99% effective, i.e. as if these numbers were accurate and meaningful. But remember, whenever you see percentage number, be it 1% or 99%, you should be aware that the number has been rounded off and “coaxed” into an easily remembered almost “insignia” intended to convey some credence, loyalty and support.
These percentages, rates and numbers are not part of nature, nor of any true scientific discovery, but rather are foolhardy and lazy attempts to arm us some “pap” “nickname” or numerical handle based upon their presumption that we are sufficiently uncaring about accuracy (and mathematical underpinnings).
Indeed, there are relatively few numbers that are near exact. I love pi (at) because mathematicians know it almost exactly to a million decimal places and which is known, for short as 3.14 or 3.14159 26535 89793 23846. ... Similarly mathematicians have been able to calculate trigonometric ratios to essentially exact numbers, as with logarithms, Benford's Law's ratios, etc.
But when you see and hear that some panacea or “cure” has a 99% effective rate, the fact that no further digits follow the decimal to succeed the “99" becomes proof of the rounding, haphazard work and utter sloppiness. If the number were more or less exactly 99%, it would read “99.000000.” If it does not, then we know that it is “sloppy guess” passed on to us because of our presumed ignorance, and lack of acumen.
Essentially any rate, percentage or average “bandied” about in the public respecting virtually any topic, is a crude stereotype playing up to our naivete and our passion to over simplify things. Any rate, at all, were the spokesperson honest, would be dependent on time, region, setting, etc. If someone suggested that the crime rate has increased 29% over the past decade, we might query: Which crime: Arsons, first degree murders, violent rapes, car thefts, illegal lottery, retail theft, etc. We might ask which Country, which region of the country ; whether urban, rural, or suburban, etc. In a sense, every rate is a stereotype which includes many foolish assumptions; dishonest lumping of disparate statistics, etc. Indeed, most of us are too unmotivated, numbed and unaware to care.