Warren Buffett’s Berkshire Hathaway now commands a 20% stake in Occidental Petroleum, after plowing another $390 million into the energy giant Warren Buffett''s Berkshire Hathaway raised its stake in Occidental Petroleum to over 20%. Berkshire bought 6.7 million shares, lifting its position to 188 million shares. Buffett''s company also holds $10 billion of Occidental''s preferred stock, and 83.9 million warrants. Warren Buffett''s Berkshire Hathaway snapped up about 6.7 million shares of Occidental Petroleum in three days this month, boosting its stake to over 188 million shares or 20.2% of the energy company, a SEC filing revealed on Monday. The famed investor''s company spent about $391 million on the latest batch of shares, lifting its total investment in the oil-and-gas explorer and producer this year to well over $9 billion. Now that Berkshire has reached the 20% ownership mark, it has the option to report a proportional share of Occidental''s profits as its own under the equity method of accounting, as it does with Kraft Heinz and Pilot Travel Centers. On the other hand, it may treat the position as a passive holding, as it does with its over 20% stake in American Express, and not alter its accounting.