Trygve Haavelmo's 1944 article ‘The Probability Approach in Econometrics’ is considered by most to have provided the foundations for present day econometrics (Morgan, 1990, Chapters 8 and 9). Since Haavelmo (1944), extraordinary advances have been made in econometrics. However, over the last two decades the efficacy and scientific status of econometrics has become questionable. Not surprisingly, the growing discontent with econometrics has been accompanied by a growing interest in econometric methodology.