At a theoretical level it was argued that econometric relations invariably lack the
necessary ‘microfoundations’, in the sense that they cannot be consistently derived from
the optimizing behaviour of economic agents. At a practical level the Cowles Commission
approach to the identification and estimation of simultaneous macroeconometric models
was questioned by Lucas and Sargent and by Sims, although from different viewpoints.
(Lucas, 1976, Lucas and Sargent (1981), and Sims (1980)).