Peter Mackey has left his position as director of the Office of Benefits and Investments for the $65 billion Federal Retirement Thrift Investment Board, Washington, said Jeannette Webber, a spokeswoman. She declined to say why Mr. Mackey left. His position has been combined with the Office of Benefits and Program Analysis and will be led by James Petrick, Ms. Webber said. Mr. Petrick formerly worked in the general counsels office. Allisone Clarke, the former head of the Office of Benefits and Program Analysis, retired, Ms. Webber said.