Berkshire's stake in Occidental has now reached 20.8% after steadily increasing the bet over the past few months. In August, Berkshire received regulatory approval to purchase up to 50%, spurring speculation that it may eventually buy all of of Houston-based Occidental. Shares of Occidental retreated 18% over the past month as oil prices dropped on rising recession fears. Berkshire also holds warrants to buy another 83.9 million common shares for $5 billion, or $59.62 each. The Berkshire stake in Occidental would rise to 27.4% if it exercised those warrants.

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