NEW YORK: Billionaire investor Warren Buffett has taken a $1 billion stake in Apple, whose stock has been in an extended slump. The stake was revealed in a regulatory filing by Buffett’s holding company Berkshire Hathaway after Apple shares skidded last week to their lowest level in two years. The filing did not indicate when Buffett purchased the shares or his reasons, but Buffett is renowned as a ‘value’ investor who takes positions in firms which trade below what he sees as their fair value. The filing with the Securities and Exchange Commission showed Berkshire with a holding of 9.8 million Apple shares at a value of around $1.07 billion. Apple has been under pressure as a result of slowing iPhone sales, threatening its chief revenue and profit source.