In his much-anticipated annual letter to stockholders , Warren Buffett, chairman and CEO of Berkshire Hathaway, celebrated his golden anniversary of ownership of the company and teases about talk of a successor — making it clear that gender is not a factor. The Oracle of Omaha sized up the U.S. economy and takes a genial swipe at "preachers of pessimism." Buffett reported that the per-share value of the company he bought in 1965 has rocketed from $19 to $146,186. That, he noted in passing, amounts to a "rate of 19.4 percent compound annually." As for 2014, Buffett reported a $18.3 billion gain in net worth. The 84-year-old billionaire described how Berkshire shifted over the years from being primarily a vehicle for investment to owning and operating businesses — and that, he says, is how it ought to be. "The unconventional, but inescapable, conclusion to be drawn from the past fifty years is that it has been far safer to invest in a diversified co...