I actually think a 'magic number' is pretty useful, as a ballpark figure. Like BMI... nobody is arguing that BMI is a gauge of health for every individual, bu

I actually think a 'magic number' is pretty useful, as a ballpark figure. Like BMI... nobody is arguing that BMI is a gauge of health for every individual, but it's a reasonable starting point, and if you want to studies of a bunch of people, well, something like BMI is pretty much required. I mean, weight in kg divided by your height in meters squared is obviously wrong and stupid in a lot of ways, but it's a lot better than nothing, and most importantly, it's super easy to understand. Having a simple answer is really useful... sometimes a simple answer, assuming that simple answer is still useful, is better than a complex answer, even when the complex answer is more correct. Sort of how bandwidth is charged for on the 95th percentiles (or on total transfer, which is in essence charging for average use)