Order Reprints Print Article George Joseph, the chairman of Mercury General Corp., working in his office in Los Angeles in 2012. Jae C Hong/AP/Shutterstock At 90, Berkshire Hathaway CEO Warren Buffett isn’t the oldest major corporate chieftain in the country. That title probably belongs to the 99-year-old George Joseph, chairman and controlling shareholder of Mercury General (ticker: MCY). Joseph remains active at the California auto insurer, sharing the leadership reins with the CEO, Gabriel Tirador. Joseph might also be the world’s oldest billionaire, with a net worth estimated by Forbes at $1.6 billion. He founded Mercury in 1961—four years before Buffett took control at Berkshire—and...