The early thirties brought what liberal economists called the Great Depression and Marxist economists described as the great crisis of capitalism. It dawned on me that the economic world order was unreliable, unstable, and, most of all, iniquitous. I sought intellectual contacts and friendship with a group of socialist students and also with a small handful of communist-oriented students and unemployed workers.
"Tjalling C. Koopmans - Biographical". Nobelprize.org. Nobel Media AB 2013. Web. 9 Jun 2014.