Dutch American mathematician and economist, who won with Leonid Kantorovich the 1975 Nobel Prize in Economic Science.
He was as the youngest son of Sjoerd Koopmans (22 June 1877, Oppenhuizen, Wymbritseradeel – 19 Oct 1959 8 PM, Hilversum), a Christian head schoolmaster and Wijtske van der Zee (12 February 1878 11h30 AM, Sneek, – 22 May 1952, 12h30 PM Hilversum). His elder brothers were Jan Koopmans (Sliedrecht, 26 May 1905 – Amsterdam, 24 March 1945, Amsterdam), who became a PhD theologian and Hendrik Koopmans (13 August 1907, Sliedrecht – 12 July 1992, Zeist), who became a chemical engineer.
His brother Jan Koopmans had connections with the “Bekennende Kirche” (Confessing Church) in Germany and became a political activist during WW2. Since 1941 he worked in Amsterdam and tried to help Jewish people. At the end of the war he had to hide. On 12 March 1945, Jan was hit in his head by a lost bullet, during the execution of 24 innocent civilians, as a reprisal for the killing by resistance fighters of an SD agent in his street. Twelve days later, he died of his injuries. At that time his brother Tjalling was in the USA.
It is of interest that the Frisian name Tjalling derives from the German name Detlef, meaning “Son of the people”. The name is associated with the Nordic mortal helper of Thor Thialfi. The surname “Koopmans” means (son of a) merchant. Because the English American speaking people could not pronounce the name “Tjalling” and called him “Charles”, he added the name Charles when he was naturalised as an American citizen in 1946. Charles or Karl means “free man” or “to rub; to be old; grain.”.
Tjalling Koopmans was a bright and musical student (composed music and played the violin), that could study Mathematics and Physics in Utrecht from age 17 until age 26 with a stipend by a private foundation — the St. Geertruidsleen stipend. He had many interests, even considered to study psychiatry, but switched in 1930 from pure mathematics to theoretical physics. With the help of professor Hans Kramers he published a classical paper on quantum mechanics “Uber die Zuordnung von Wellenfunktionen und Eigenwerten zu den einzelnen Elektronen eines Atoms’ (Physica 1, 1934) and graduated cum laude on 7 July 1933 on Mathematics and Physics.
Via Kramers he also met the once physicist, later econometrist Jan Tinbergen in 1934, and started to apply mathematics on economical questions. He and Tinbergen hoped that the adaptation of mathematical statistical models could help to improve the economy in times of crisis. Via Hans Kramers he also became befriended with the left wing historians Jan and Annie Romein and later he wrote that “Das Kapital” was the first economic book that he had studied. In 1935 he spent some years in Oslo with Noble Prize winner Ragnar Frisch. On 26 November 1936 he dissertated in Leiden with “Linear regression analysis of economic time series” under Tinbergen and Kramers. He joined Tinbergen at the higher Economical School (now Erasmus University) in Rotterdam and also helped him with his work for the League of Nations in Geneva (1938).
On 22 October 1936 he married in Amersfoort, Trijntje “Truus” Wanningen, (1912, Amersfoort – 2002), an economist. They would have three children: Anne Koopmans Frankel (April 1940, Geneva), a PhD biologist, Helen (1946) and Henri W. Koopmans (28 January 1944, Washington DC – 17 April 2010, Rosedale Hospice Calgary), a PhD. psychologist.
After the German attack on Norway (9 April 1940), he and his wife decided to emigrate to the USA. Since May 1940 Holland was occupied and the geopolitical situation changed every day. On 4 June they tried to go to Genua, later that day they heard of an American ship in Bordeaux, France and could arrive with the SS Washington in New York on 11 July 1940.
In the USA Tjalling Koopmans got research jobs and began to study methods for allocating shipments between sources and destinations such that total cost would be minimized. This so-called transportation problem was a special case of what subsequently became known as linear programming. Ship capacity (being undermined by submarines) became strategically crucial as soon as the USA became involved in WW2. The Soviet mathematician and economist Leonid Kantorovich (19 January 1912, Saint Petersburg, – 7 April 1986, Moscow), known as the founder of linear programming, studied the same subject with regard to the for the Soviets important railways. Both Kantorovich and Koopmans were awarded the 1975 Nobel Prize in Economics for their theories and development of techniques for the optimal allocation of resources.
After WW2 Tjalling Koopmans became director of the Cowles Commission for Research in Economics in Chicago (July 1948). On July 1 1955 he became professor of Economics at Yale. Tjalling Koopmans remained with Yale and the Cowles Foundation the rest of his academic career, serving for a period as the director of the Cowles Foundation.
Tjalling Koopmans died in 26 February 1985 at age 75 after a series of cerebral strokes in the last months of 1984.

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