Warren was born in Seattle and attended Ballard High School. He then attended the UW for his undergraduate and graduate degrees in sociology. He became the Director of the Oregon State Census Board and Assistant Professor at Portland State University. He moved to Alberta, Canada to become Associate Professor in 1964 and a full Professor at the University of Alberta. Next he moved to Arizona in 1967 as a Professor in Sociology at the University of Arizona until 1969.

He returned to Toronto as Professor of Sociology at the University of Toronto and also Associate Chairman for Sociology which he held until his retirement in 1988. He also founded the Population Research Laboratory and was its director for 20 years. At retirement he was granted the title of Professor Emeritus by the University of Toronto.

Warren was a demographer and sociologist. He is well known in Canada and internationally for his work on Canada’s population and immigration. Throughout his academic life he was active in demographic research with particular reference to the impact of immigration and ethnic diversity on the Canadian population. He published two major census monographs, two widely used textbooks, numerous chapters in books, research papers and articles in journals. His work was influential in the formulation of immigration and demographic policies. He served as a consultant to various government and other agencies concerned with population questions. Among the many awards and honors he received, Warren was elected to the Royal Society of Canada in 1989.