The Oracle of Omaha has spent over $63 billion since mid-2018 buying a stock that doesn't show up in Berkshire Hathaway's 13F filings or investment portfolio.
Occidental Petroleum (OXY) closed at $64.79 in the latest trading session, marking a +1.03% move from the prior day.
American Express, one of the world's top credit card companies, has also long been a favorite of Berkshire Hathaway CEO Warren Buffett.