What an investor needs is the ability to correctly evaluate selected businesses. Note that word โselectedโ: You don't have to be an expert on every company, or even many. You only have to be able to evaluate companies within your circle of competence. The size of that circle is not very important; knowing its boundaries, however, is vital.
Warren BuffettI mean, Hank Paulson is in there [ Treasury] at the wrong time, probably shouldn't have taken the job. He's a friend of mine. But he knows markets, he knows corporations' work, he knows money, and he's got the interests of the country at heart.
Warren Buffett