There's a clear reason for the giant discrepancy between the amounts bought and sold in the portfolio. Valuations in the market have climbed considerably higher over the last few years, particularly among the large-cap stocks held in Berkshire's portfolio.Meanwhile, additions to the portfolio have been relatively small. Most investments involved adding a few hundred million dollars to existing positions. The biggest new positions are Chubb , Alphabet , and Sirius XM . The company also increased its stake in ...