Alan Greenspan, the influential economist who led the Federal Reserve for nearly two decades and became one of the most powerful figures in global finance, died Monday morning at the age of 100. His wife, veteran NBC News journalist Andrea Mitchell, told CNBC that Greenspan died from complications of Parkinson’s disease. The couple, who married in 1997, had been together for nearly three decades. Greenspan served as Fed chairman from 1987 to 2006 under four presidents — Ronald Reagan, George H.