AshokanMtn · CC BY-SA 4.0

Klein built the statistical models that gave Keynesian economic theory a working, quantitative form — computer simulations of the economy that central banks, including the Federal Reserve, still use to forecast fluctuations and test policy before enacting it. For creating econometric modeling and applying it to real economic analysis, he was awarded the 1980 Nobel Memorial Prize in Economic Sciences, work Harvard economist Martin Feldstein credited with turning Keynesian ideas into practical, testable tools.