I’m not sure that I fully grasped the overwhelming importance of our peer group until I came across a fascinating book and a subsequent TED talk by Nicholas Christakis. He and his colleagues at Harvard had studied obesity in human networks, and this research led them to an important discovery: if you have obese friends, you’re more likely to be obese. Similarly, if you have fit and healthy friends, you’re more likely to be fit and healthy. In other words, our close social connections count not only in the obvious ways, but also in subtle ways that we barely understand." The Education of a Value Investor Guy Spier