Trygve Haavelmo won the 1989 Nobel Memorial Prize in Economic Sciences for his clarification of the probability foundations of econometrics.
Haavelmo argued that economic relationships should be formulated and tested within a probabilistic framework. His ideas helped economists distinguish theoretical relationships from observed statistical outcomes and gave econometric analysis a more rigorous basis for dealing with uncertainty, simultaneous relationships, and imperfect data. His 1944 work became especially influential in the development of modern econometrics.
Haavelmo received the prize alone in 1989. He is sometimes confused with Lawrence Klein, whose 1983 prize recognized the construction and application of econometric models. Robert Engle and Clive Granger shared the 2003 prize for methods involving time series, decades after Haavelmo established foundational principles.