Why do various websites, as well as doctor growth charts, say that a male will stop growing by the time he is 20? Should I stick with the Tanner stage information of a male typically ceasing to grow by the time he is 17?
The vast majority of males do stop growing by 20, but there are exceptions. There are cases of men still growing while in their twenties. I could not find any statistics on it, but I suspect that it is less than 1% of the population.
Dr. Tanner used an narrower cut off, aiming to cover 95% of all children. That leaves 5% outside of the ranges he gave. [Variations in the Pattern of Pubertal Changes in Boys].
So what this means is that 95% of all males stop growing by age 17?
The range of 15 to 20 covers 95% of all males. If you average all males, you get the age of 17 for reaching stage 5, which is the point when you stop growing in height.