You know that frame you can make by using your index and thumb?
I wonder what the actual average aspect ratio is. If you standardized what it means to make this frame, e.g. must align tangent of thumb apex with tangent to index finger, then what would the actual average be?
I started myself by getting a bunch of friends and I's traceouts of what the inner part looked like, e.g.
Now comes the hard part of defining how to find the actual bounding box these refer to. Do we take the bounding box to be tangent to extremities of the outside or the inside. Then you'll have each individual's aspect ratio, and can get to answering the interesting questions like what the average and population distribution is (is it normally distributed??).