Koopmans, Tjalling Charles (tyälˈĭng, kōpˈmäns, –mənz) [key], 1910–85, American economist, b. Graveland, the Netherlands. Raised and educated in the Netherlands, he came to the United States in 1940 and became interested in the economics of transport costs while working for the British Merchant Shipping Mission. He was a professor of economics at the Univ. of Chicago (1944–55) and Yale Univ. (1955–81). As a result of his work on the allocation of resources, he shared the 1975 Nobel Memorial Prize in Economic Sciences with Leonid Kantorovich. He wrote Three Essays on the State of Economic Science (1957).