Thanks for the link. My aim is not really to dissuade anyone from diversifying. Rather, it is to focus on the quality of the businesses one is invested in. I think investors who diversify for the sake of diversifying risk losing sight of the businesses they own. Many successful investors do diversify, but I would propose that this is often, in some sense, accidental. For example, selecting strong businesses with distinct competitive moats implies that they cannot effectively compete with each other. Therefore, one would expect them to respond differently to unsystematic events.