INFORMS News: In Memoriam — Thomas L. Saaty (1926-2017)

Thomas Saaty

By Arjang Assad and Luis G. Vargas

Thomas L. Saaty, Distinguished Professor at the University of Pittsburgh, member of the National Academy of Engineering, and creator of the decision-making mechanisms Analytic Hierarchy Process (AHP) and Analytic Network Process (ANP), passed on Aug. 14. He was 91 and remained a creative and passionate researcher until the end.

Tom was born in Mosul, Iraq, on July 18, 1926. His parents were descendants of Assyrian Christians from northern Iraq. Tom’s father, David, lived in Rhode Island for many years but returned to his home town of Mosul in the early 1900s. David was a well-known entrepreneur; he opened the country’s first ice-making factory in 1923. His ambition was to modernize Iraq. David’s marriage to Dola in 1925 produced four children: Tom, John, Ben and Grace. Tom was the first child.

Tom went to Brummana High School in Lebanon, a Quaker school, when he was 15. Upon graduation, he attended the American University of Beirut for two years. He came to the United States as a youth of 19 to attend Columbia Union College in Takoma Park, Md. He went on to receive an M.S. degree in physics from the Catholic University of America. In 1953, he received a Ph.D. in mathematics from Yale University under the supervision of the functional analyst Einer Hille. Tom’s dissertation was on the Bessel Tricomi equation. He conducted postgraduate studies for a year in Paris, at the Sorbonne, under the direction of the algebraic topologist Henri Cartan.

After graduating from Yale, and, despite efforts by Einer Hille who wanted Tom to stay at Yale to do research, he joined Melpar, Inc. as a scientific analyst studying submarine defense until 1954. He then joined the Operations Evaluation Group (OEG) in Washington D.C. OEG was formed in 1945 as a successor to the World War II Operations Research Group that conducted the Antisubmarine Warfare Operations Research Group (ASWORG) organized by Philip Morse in 1942. At OEG, Tom worked on classified submarine detection problems and the mathematics of radar reconnaissance, a topic of interest due to U.S. aircraft flights (RB48 and U-2) over the Soviet Union. This period also produced Tom’s first papers in Operations Research. The 1954 paper resulted from joint work on parametric programming at project SCOOP with Saul Gass. Tom’s survey of queueing theory appeared in Operations Research in 1957.

In 1958, Tom was appointed scientific liaison officer to the U.S. Embassy in London. His 1959 book, “Mathematical Methods of Operations Research”, was the result of his international travels and served as the first graduate level text on the subject. In 1959, he was named director of advanced planning in the Office of Naval Research (ONR), a post he held until 1961 when he was appointed as scientific analyst in the Arms Control and Disarmament Agency (ACDA), Department of State. He stayed in ACDA during 1963-1969. He then left to start his academic career at the University of Pennsylvania. In 1979, Jerry Zoffer, then dean of the business school at the University of Pittsburgh, recruited Tom to the university, where he held a Distinguished University Professor Chair. For the next 38 years, Tom was the most widely known member of the Joseph M. Katz Graduate School of Business, with several affiliated appointments in other academic units of the university. During his long tenure at the Katz school, his fame spread internationally. He traveled widely across the globe, and scholars and students from several countries came to Pittsburgh to work with Tom.

Tom was trained in pure mathematics and published several volumes in that area. He then turned his attention to writing books on subjects of interest to the OR community: “Elements of Queueing Theory with Applications” (1961) where he surveyed the literature; “Nonlinear Mathematics” in two volumes (1964); “Finite Graphs and Networks” (1965) and “Optimization in Integers and Related Extremal Problems” (1970). Tom’s book with George Dantzig, “Compact City” (1973), was part of O.R. lore for many years.

Tom is best known for his theory of the Analytic Hierarchy Process (AHP) and its extension to the Analytic Network Process (ANP). Tom developed AHP based on his work at the U.S. State Department’s Arms Control and Disarmament Agency during the Kennedy and Johnson administrations. AHP is a general methodology to derive ratio scales from pairwise comparisons in a multilevel hierarchical structure. It allows alternatives in complex decision problems to be ranked using an intuitively appealing procedure. It has proven to be remarkably versatile in the range of its possible applications.

The first major application of AHP was reported in Tom’s 1977 paper in Interfaces; it addressed the ranking of infrastructure projects in the Sudan. Tom described the mathematical principles underlying AHP in his book “The Analytic Hierarchy Process: Planning, Priority Setting, Resource Allocation” (1980). He continued to author another two dozen books on the subject. In 2008, Tom was awarded the INFORMS Impact Prize “for his seminal work on the Analytic Hierarchy Process, and for its development and extraordinary impact.”

Tom’s past experience in government and arms control made him passionate about conflict resolution, and in particular, finding a solution for the Israeli-Palestinian Middle East conflict. Starting in 2009, he organized seminars with representatives from both sides to a promising mutually acceptable solution that leveraged the AHP/ANP methodology. An account of this multi-year project is planned to appear in book form.

Creativity, especially in applications of mathematics, was Tom’s passion. He cultivated it in his own research across a remarkably diverse collection of fields. He also loved teaching the creativity course at the Katz school, challenging students to think outside the box. Students who appreciated this challenge remembered him as a remarkable mentor. His book, “Creative Thinking, Problem Solving and Decision Making” (2001), ties together his main pursuits and interests in this area. Tom also was intrigued in decision-making in the brain. He introduced an extension of his discrete eigenvalue model for AHP to continuous spaces to model cognitive brain activity using this approach. He dedicated most of his time until his death to this problem.

Tom was elected a fellow of the American Association for the Advancement of Science (AAAS) in 1959 and, in 1970, to the Spanish Royal Academy of Mathematical, Physical and Natural Sciences. His election to the National Academy of Engineering came in 2005. His other awards include the Gold Medal of The International Society on Multiple Criteria Decision Making (2000) and the International Quality Function Deployment Akao Prize from Japan (2007). At the University of Pittsburgh, Tom received the Chancellor’s Distinguished Research Award, the highest award for research at the university. His cumulative Google Scholar citation count exceeded 97,000 citations.

Tom loved music and humor. He possessed CDs and records of all of Beethoven’s works and, at one point in his life, could identify any work by Beethoven. When he was younger, he realized that he was not good at telling jokes. He decided to improve his abilities as a raconteur of jokes. This led to his compilations of hundreds of jokes into many booklets under a wide variety of pseudonyms. He took special pleasure in sharing these collections with colleagues, friends and students.

Tom is survived by his wife, Rozann Saaty; his children, Linda, Michael, Emily, John and Daniel; his grandchildren, Tom, Michael, Meghan, Amy, Kara, Monica, Emma, Nina, Max and Fletcher; and his great grandchildren, Lydia, Fiona and Lilly.

Arjang Assad is professor and Henry E. Haller Jr. Dean of the Joseph M. Katz Graduate School of Business and College of Business Administration at the University of Pittsburgh. He is a current member and past chair of the INFORMS History & Traditions Committee.

Luis G. Vargas is professor of Business Analytics & Operations at Joseph M. Katz Graduate School of Business and College of Business Administration at the University of Pittsburgh. He has co-authored several books and numerous papers with Tom Saaty.