Passage: After graduation in 1979, Rometty went to work for General Motors Institute in Detroit, where she was responsible for application and systems development. In 1981 she joined IBM as a systems analyst and systems engineer in Detroit. Initially working with clients in the insurance industry, she spent her first ten years at IBM in technical positions. The New York Times writes that she "quickly moved up to a series of management jobs," where she worked with clients in insurance, banking, telecommunications, manufacturing and health care. She spent the 1990s working in sales,  and by the late 1990s was helping clients such as Prudential Financial, Inc. with their internet features. She joined IBM's Consulting Group in 1991.

Question: When did she join IBM?
1991