Kim C. Border (BS '74), a longtime professor of economics at Caltech, passed away November 19. He was 68 years old.
"Kim was a dedicated teacher and a very generous colleague," says Jean-Laurent Rosenthal (PhD '88), Caltech's Rea A. and Lela G. Axline Professor of Business Economics and the Ronald and Maxine Linde Leadership Chair of the Division of the Humanities and Social Sciences. "He was always willing to share his deep knowledge of economic theory. He was also curious about many things well beyond the domain of mathematical economics. His quiet dedication to being a helpful member of the division was appreciated by everyone. Above all, he cared about people, and although he liked to tease, he really worked to make everyone feel welcome and engaged."
"Kim was a good friend. He was honest and straightforward and willing to do anything to help his colleagues," says John Ledyard, the Allen and Lenabelle Davis Professor of Economics and Social Sciences, Emeritus.
Federico Echenique, the Allen and Lenabelle Davis Professor of Economics, says that Border was an "amazing colleague" and "very generous with his time and intelligence." He says Border was always willing to sit down with colleagues and students and explain economic principles.
Border's colleagues also described him as a "Caltech guy," who knew "everybody and everything about the Institution." Says Echenique, "He knew all the past division chairs and the years they served, every course requirement change, he remembered all the students, etc." A Caltech alumnus, Border received his bachelor's degree from Caltech in 1974 and his PhD in economics from the University of Minnesota in 1979. He joined the Caltech faculty more than 40 years ago, in 1979.
Border specialized in decision theory and sought to better understand how and when people behave rationally when presented with risks. Ledyard says that Border's work in this area, in particular on an economic model called expected utility theory, was "fundamental in deep and important ways."
Border also worked in an area known as both incentive and institutional design. He applied insights from mathematical areas to design incentives to solve resource allocation problems; for example, his research helped in the design of auctions, such as those for greenhouse gas permits or online advertising. In 1991, Border derived a mathematical statement, now known as Border's theorem, that put constraints on what can and cannot be done in auctions. The theorem is widely used today and has sparked a "lively literature that engages both economists and computer scientists," says Echenique.
"Kim's theorem greatly simplifies mechanism design, in particular the search for desirable economic institutions, or different ways of organizing a market," he says. "His work is very important to the field today."
Border also contributed to the study of a social science problem related to voting theory. His starting point was Arrow's impossibility theorem, named after the late Nobel Laureate Kenneth Arrow. The theorem points out flaws in a ranking-based voting system. It states that the preferences of individuals cannot be translated to a community-wide ranking of priorities under certain conditions. According to Echenique, Border figured out a way to avoid the conclusion of Arrow's theorem in the types of environments that political scientists use to model, for example, Congress. The message, in short, is that "democracy is possible," he says.
Border was the author of three textbooks, including Infinite Dimensional Analysis: A Hitchhiker's Guide (1994), which has been reprinted several times. Ledyard called the book "beautiful," and says that Border was an exceptional writer.
"Every theorist I know owns his books," says Echenique. "Partly this is because his writing was so crystal clear and engaging." As an example of Border's writing, Echenique referenced one of Border's articles, published in 1987 and titled "Samurai Accountant: A Theory of Auditing and Plunder." The study analyzes a situation common in the practice of tax collecting, where somebody wishes to extract wealth from somebody else who is reluctant to part with it and has more information than the extractor about how much money they have. In the paper, Border wrote, "Consider the situation described by Kurosawa (1970) [a reference to a film directed by Akira Kurosawa] where a band of brigands assails a peasant village and demands tribute. The brigands can plunder the village, but this can be costly, particularly if the village harbours masterless samurai."
"I wish I could write papers like that," Echenique says.
Border was the director of graduate studies for social sciences from 1994–96; the executive officer for the social sciences from 1995–99; and the chair of the faculty from 1999 to 2001. He was on the editorial board of Economic Theory from 1990 to 2000 and was a panelist at the National Science Foundation's Research Fellowship Program in 2003 and 2004.
He is survived by his son Richard.
An abbreviated version of this obituary was originally published on November 21, 2020.