ABSTRACT
In 1949 two papers by D. Cochrane and G.H. Orcutt introduced a range of problems connected with dynamic, linear models that are still being studied. Avoiding such hyperbole as the occasion might induce it may fairly be said that the papers were important. The papers dealt with two problems, namely that arising from the fact that there may be many endogenous variables (or outputs) connected by as many simultaneous relations, and that arising from autocorrelation of the disturbances in the equations. A third problem, mentioned but not discussed, is that of errors of measurement in the exogenous variables (inputs). We shall discuss this only briefly.
