Should this be a relative measurement?
The way I determine the length of a short bow (for my kids, friends, etc.) is to measure the distance between the base of the sternum and the ground. I'm 68" and a shortbow (for me) is 47"-48". If the average male height is 70", then average shortbow would be 49"-50".
Coincidently, the short-bow archer in the picture is drawing the arrow to the chest, and his anchor point is the base of the sternum.
(Also, for those of you like to "investigate" this kind of stuff, you'll notice the length of the shortbow in the picture is (approx.) the distance between his anchor point and the bottom of his feet
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