David Blackwell

David Harold Blackwell (April 24, 1919 – July 8, 2010) was an American statistician and mathematician who made significant contributions to game theory, probability theory, information theory, and statistics. He is one of the eponyms of the Rao–Blackwell theorem, and is also known for the Blackwell channel, Blackwell's contraction mapping theorem, Blackwell's approachability theorem, and the Blackwell order. He was the first African American inducted into the National Academy of Sciences, the first African American full professor with tenure at the University of California, Berkeley, and the seventh African American to receive a Ph.D. in mathematics. Blackwell was also a pioneer in textbook writing. He wrote one of the first Bayesian statistics textbooks, his 1969 Basic Statistics. By the time he retired, he had published over 90 papers and books on dynamic programming, game theory, and mathematical statistics. In 2012, President Barack Obama posthumously awarded Blackwell the National Medal of Science.

David Harold Blackwell was born on April 24, 1919, in Centralia, Illinois, to Mabel Johnson Blackwell, a full-time homemaker, and Grover Blackwell, an Illinois Central Railroad worker. He was the eldest of four children with two brothers, J. W. and Joseph, and one sister, Elizabeth. Growing up in an integrated community, Blackwell attended "mixed" schools, where he distinguished himself in mathematics. During elementary school, his teachers promoted him beyond his grade level on two occasions. It was in a high school geometry course, however, that his passion for mathematics began. An exceptional student, Blackwell graduated from high school in 1935 at the age of sixteen.

Blackwell entered the University of Illinois at Urbana-Champaign with the intent to study elementary school mathematics and become a teacher. He was a member of Alpha Phi Alpha, a black fraternity that housed him for his full six years as a student. He earned his bachelor's degree in mathematics in three years in 1938 and, a year later, a master's degree in 1939. He was awarded a Doctor of Philosophy in mathematics in 1941 at the age of 22. His doctoral advisor was Joseph L. Doob. At the time, Blackwell was the seventh African American to earn a Ph.D. in mathematics in the United States and the first at the University of Illinois at Urbana-Champaign. His doctoral thesis was on Markov chains.

Blackwell completed one year of postdoctoral research as a fellow at the Institute for Advanced Study (IAS) at Princeton in 1941 after receiving a Rosenwald Fellowship, which was a fund to aid black scholars. There he met John von Neumann, who asked Blackwell to discuss his Ph.D. thesis with him. Blackwell, who believed that von Neumann was just being polite and not genuinely interested in his work, did not approach him until von Neumann himself asked him again a few months later. According to Blackwell, "He (von Neumann) listened to me talk about this rather obscure subject and in ten minutes he knew more about it than I did."

While a postdoc at IAS, Blackwell was prevented from attending lectures or undertaking research at nearby Princeton University, which the IAS has historically collaborated with in research and scholarship activities, because of his race.

Seeking a permanent position elsewhere, he wrote letters of application to 104 historically black colleges and universities in 1942, and received a total of only three offers. He felt at the time that a black professor would be limited to teaching at black colleges. Having been highly recommended by his dissertation advisor Joseph L. Doob for a position at the University of California, Berkeley, he was interviewed by statistician Jerzy Neyman. Neyman supported his appointment, and Griffith C. Evans, the head of the mathematics department, at first agreed and even convinced university president Robert Sproul that it was the correct decision, only to subsequently balk, citing the concerns of his wife. It was customary for Evans and his wife to invite the members of the department over for dinner and "she was not going to have any darkie in her house."

He was offered a post at Southern University at Baton Rouge, which he held in from 1942 to 1943, followed by a year as an Instructor at Clark College in Atlanta.

Blackwell joined the Mathematics Department at Howard University in 1944. When he joined, he was one of four faculty members and within three years he was appointed full professor and head of the department. He remained at Howard until 1954. In 1947, while at Howard, Blackwell published the paper "Conditional Expectation and Unbiased Sequential Estimation", which outlined a technique that later became known as the Rao–Blackwell theorem. The theorem provides a method for improving statistical estimates by potentially reducing their mean squared error.