The key question for investments is: "How strong is a company's competitive advantage, and how sustainable is it?"

Warren Buffett agrees, noting in a 1999 Fortune article: "The key to investing is not assessing how much an industry is going to affect society, or how much it will grow, but rather determining the competitive advantage of any given company and, above all, the durability of that advantage. The products or services that have wide, sustainable moats around them are the ones that deliver rewards to investors."

Perhaps related is one of Mr. Buffets other interesting quotes that says he is like a hedgehog, which knows only one thing, but that one thing is a big thing. Others are trying to know many things, most of which are naturally small, and because valuing the sheer number they can't distinguish the important big thing from all the small things.