Berkshire owns a number of insurance companies, which are strongly cash-generative, since the nature of insurance is that the payment of premiums precedes the payment of claims. These funds, and Berkshire’s retained earnings, are invested in a portfolio of wholly owned businesses and large holdings in some listed companies. The distinguishing characteristic of all these businesses is that they have sustainable competitive advantages: market positions competitors would find it difficult or impossible to reproduce. There is little portfolio turnover. The preferred holding period for stocks is, Mr Buffett has often said, forever.