Why do short people live longer?

Rather than listening to theories and arguments, just look at the older population and you'll have the answer. Sure, each new generation has been getting taller over the last few hundred years, and we shrink a little as we age. But we don't shrink quite enough to explain why most centenarians are so much shorter than average - somewhat shorter than average for their generation. Of course there are always exceptions. Also, for a quicker study, dogs and humans have many parallels - one being that medium and smaller dogs tend to live longer than very large dogs.