Greg Abel Has 75% of Berkshire Hathaway's Portfolio Invested in Just 8 Stocks. Is the 1 That's Lagging Behind the S&P 500 the Best Buy Now?

Key Points With the exception of American Express, Berkshire's top stocks have performed well during the past year. Cardholder perks and marketing expenses are eroding American Express' margins. American Express depends on cardholders' discretionary spending, making it vulnerable to economic downturns. 10 stocks we like better than American Express › It hasn't even been a year since Warren Buffett made Greg Abel chief executive officer of Berkshire Hathaway (NYSE: BRKA) (NYSE: BRKB) .