The game of investing is one of making better predictions about the future than other people. How are you going to do that? One way is to limit your tries to areas of competence. If you try to predict the future of everything, you attempt too much.

At Berkshire Hathaway we do not like to compete against Chinese manufacturers.

[In picking stocks] You really have to know a lot about business. You have to know a lot about competitive advantage. You have to know a lot about the maintainability of competitive advantage. You have to have a mind that quantifies things in terms of value. And you have to be able to compare those values with other values available in the stock market.

A different set of incentives from rising in an economic establishment where the rewards system, again, the reinforcement, comes from being a truffle hound. That's what Jacob Viner, the great economist called it: the truffle hound - an animal so bred and trained for one narrow purpose that he wasn't much good at anything else, and that is the reward system in a lot of academic departments.

And maybe the cereal makers by and large have learned to be less crazy about fighting for market share-because if you get even one person who's hell-bent on gaining market share.... For example, if I were Kellogg and I decided that I had to have 60% of the market, I think I could take most of the profit out of cereals. I'd ruin Kellogg in the process. But I think I could do it.

Well, the questioner came from Singapore, which has perhaps the best economic record in the history of developing an economy. And therefore he referred to 15 percent per annum as modest. It's not modest, it's arrogant.

The idea of excessive diversification is madness. Wide diversification, which necessarily includes investment in mediocre businesses, only guarantees ordinary results.