Arthur P. Dempster Obituary

Professor Emeritus Arthur Pentland Dempster passed away peacefully surrounded by family and close friends on January 30, 2026, at the age of 96. The Department and its members are deeply saddened by the loss of a beloved colleague and mentor whose groundbreaking scholarship and dedicated teaching inspired students for more than six decades.

Professor Arthur Dempster was born in Toronto, Canada, in 1929, to Nelson J. Dempster, a World War I veteran, and Jessie MacAlpine. The Dempster family owned a thriving bakery business, an offshoot of a bakery originally founded by Arthur’s great grandfather James Dempster who immigrated to Canada from Glasgow, Scotland  in 1871.  Jessie was a talented pianist on track for a career as a concert pianist when she married and had three sons, John, Arthur, and Nelson. Arthur’s early interest in science and mathematics was influenced by his uncle and namesake, Arthur Jeffrey Dempster, a distinguished University of Chicago physicist known for his pioneering work in mass spectrometry that led to his 1935 discovery of uranium-235. 

Professor Dempster received a B.A. in Mathematics and Physics from the University of Toronto in 1952 and completed his Ph.D. in Mathematical Statistics at Princeton University in 1956, where he studied under John W. Tukey. While at Princeton, he met his future wife, Elizabeth O’Neill, at a Princeton/Bryn Mawr mixer. Elizabeth graduated with first class honors in classics from Queen's University in Kingston Ontario, and obtained a master’s degree in Greek at Bryn Mawr College. Upon completing her master’s, she went to the American School of Classical Studies in Athens. Arthur travelled to Athens a few months into her stay there to propose. They were married in Toronto in January 1957 while Arthur was completing a teaching appointment at the University of Toronto. The couple then moved to New Jersey where Arthur did a short stint at Bell Labs from 1957-58. While in New Jersey, they met a Polish couple, Hanka and Witold Sylvestrowicz, who became dear friends and whose influence inspired Arthur and Elizabeth’s lifelong interest in contemporary art and design. 

Professor Dempster joined the newly established Department of Statistics at Harvard University as an assistant professor in 1958 just a year after the Department’s founding. He was promoted to associate professor in 1961 and then to full professor in 1964. He was appointed Chair of the Department in 1969 and served a total of thirteen years as Chair between 1969 and 1985, with two short hiatuses. During this period he helped shape the Department’s teaching and research mission and served as an advisor, mentor, and teacher to many of the Department’s Ph.D. students.

Professor Dempster remained at Harvard until his transition to emeritus status in 2005. Over five decades of service, he taught countless undergraduates and advised nearly forty Ph.D. students, many of whom went on to be leaders in academia and industry. His dedication to research, teaching, and leadership helped build the Department into the vibrant intellectual community we benefit from today.

His pathbreaking contributions to theoretical statistics—including generalizations of Bayesian inference, Dempster–Shafer theory, multivariate statistics, and computation—are universally recognized and celebrated within statistics and across the broader scientific community. He was elected a Fellow of the Institute of Mathematical Statistics, a Fellow of the American Statistical Association, and a Fellow of the American Academy of Arts and Sciences. His 1977 paper coauthored with Nan Laird and Don Rubin, “Maximum Likelihood from Incomplete Data Via the EM Algorithm,” has been listed among Nature’s most-cited papers.

Arthur and Elizabeth warmly welcomed many colleagues and students into their beautiful Bauhaus inspired home on Moon Hill Road in Lexington and later to their home on Walker Street in Cambridge. Their hospitality helped foster the collegial environment for which the Department is known. Arthur and Elizabeth also occasionally invited students and colleagues to their summer cottage on Lake Muskoka in Ontario, Canada, a place that had been in Arthur’s family for generations and where he spent summers swimming, canoeing, sailing, and contemplating from his early childhood through his 80s. He passed on his love of nature and outdoor activities to his children and grandchildren.

In honor of Professor Dempster’s scholarship and mentorship, the Department established the Arthur P. Dempster Award in 2012, with funding support from his former Ph.D. student Stephen Blyth. Now in its fifteenth year, the Award has recognized promising graduate-student research in theoretical and foundational statistics.

Professor Dempster is survived by his wife, Elizabeth, his children Rebecca, Ben, and Sara, their spouses Matthew, Yuri, and Eloy, grandchildren Rowan, Aidan, and Gavin, nieces Mary, Cynthia, Emily and Elayne, and nephews Andrew and Timothy. The family is planning a memorial service to take place later in 2026. 

Professor Dempster will be honored with a Joint Statistical Meetings (JSM) session in Boston at 2pm on Sunday, August 2nd.

The Department has set up a Kudoboard for colleagues and the statistics community to share their reflections, memories, and photos to celebrate Professor Dempster's impact.

The public obituary and comments can be found at Keefe Funeral Home.

In lieu of flowers, the family welcomes memorial donations to one of the following organizations in honor of Arthur Pentland Dempster. Please use email rebecca.dempster@gmail.com for the family notification field on the giving page:

Muskoka Conservancy - Memorial Donation Link

Association for Women in Science - Honorary or Memorial Gift Link

WGBH Educational Foundation - Tribute and Memorial Gift Link 

This tribute to Professor Dempster was co-authored by Professor Ruobin Gong, Professor Emeritus Nan Laird, and the Dempster family. To view an extended obituary and tribute, please visit this webpage.