New York Post: Harper’s magazine CEO John R. “Rick” MacArthur has tapped 35-year-old Christopher Cox to be the new editor-in-chief of the title. Not too surprisingly, Cox, who has been at the magazine for five years, most recently as deputy editor, said he plans to reach out to new and younger writers. He replaces Ellen Rosenbush , 70, who will become an editor-at-large. She has been at the magazine 26 years, including the last five as editor-in-chief.