* Labor markets to be major focus of Fed annual retreat WASHINGTON, Aug 20 (Reuters) – Mike Yack has left the workforce twice in the last eight years and calls himself retired, yet at age 62 the former General Motors employee does not consider his working life over. Yack, who says he can get by on Social Security and his GM pension, is among millions of Americans who could re-enter the U.S. They don’t show up in the U.S.