economic efficiency and prices. Finally, the importance of the article by Koopmans (1942) deriving the distribution of the serial correlation coefficient was recognized by John von Neumann, and it later influenced the optimal tests for a unit root by John Denis Sargan and Alok Bhargava (Sargan and Bhargava, 1983). Family and name Tjalling Charles Koopmans was a son of Sjoerd Koopmans and Wytske van der Zee; his middle name Charles was probably derived from his patronymic "Sjoerds". One of Sjoerd Koopmans's sisters, Gatske Koopmans, and her husband Symon van der Meer were the paternal grandparents of Nobel Prize winner Simon van der Meer. Tjalling Koopmans and Simon van der Meer were therefore first cousins once removed. Tjalling had two brothers, one of whom was theologian Rev. Dr Jan Koopmans, who in 1940, early during the German occupation of the Netherlands, wrote the widely distributed pamphlet "Bijna te laat" ("Almost too late", 30,000 copies), warning about the future of the Jews under the Nazi regime. In 1945, towards the end of the war, he witnessed an execution of hostages in Amsterdam from behind a window and was mortally wounded by a stray bullet. Selected works Cowles Foundation Paper No. 357. Further reading See also Linear programming Transportation theory (mathematics) References External links Scarf, Herbert E., "Tjalling Charles Koopmans: August 28, 1910 – February 26, 1985", National Academy of Science IDEAS/RePEc Biography of Tjalling Koopmans from the Institute for Operations Research and the Management Sciences Tjalling Charles Koopmans Papers (MS 1439). Manuscripts and Archives, Yale University Library. 1910 births 1985 deaths People from Wijdemeren Dutch Nobel laureates Dutch economists Dutch emigrants to the United States Utrecht University alumni University of Amsterdam alumni Nobel laureates in Economics Fellows of the American Statistical Association Fellows of the Econometric Society Fellows of the Institute of Mathematical Statistics Presidents of the Econometric Society Mathematical economists Econometricians Time series econometricians General equilibrium theorists Operations researchers 20th-century American writers 20th-century American economists 20th-century American mathematicians Presidents of the American Economic Association Distinguished Fellows of the American Economic Association Members of the Royal Netherlands Academy of Arts and Sciences Dutch mathematicians