Tillerson joined Exxon in 1975, and by 1989 had become general manager of the Exxon USA central production division. In 1995 he became president of Exxon Yemen Inc. and Esso Exploration and Production Khorat Inc. In 2006, Tillerson was elected chairman and chief executive officer of Exxon, the world's 6th largest company by revenue. Tillerson retired from Exxon effective December 31, 2016, and was succeeded by Darren Woods. He is a member of the National Academy of Engineering. He resigned his position from Exxon to pursue his nomination of United States Secretary of State.