Warren Buffett

Berkshire Hathaway is controlled by Warren Buffett, who is chairman and chief executive of the company which owns a range of companies, including GEICO and NetJets, a substantial stake in Heinz, and has stakes in American Express, Procter & Gamble and IBM. The company is noted for outperforming the stock market under the leadership of Buffett, a value investor.

Amazon founder and CEO Jeff Bezos is seen in Amazon's Seattle headquarters on Monday. Amazon has announced that it will be developing a health care company for its staff - and potentially the rest of America, causing woes for the Dow index. Photo: Reuters

Amazon enters health care market - causing stock turmoil

Amazon will create a company that helps their US employees find quality health care “at a reasonable cost,” the company announced Tuesday - and in doing so caused stocks for other health care providers to tumble.