Economists have been building econometric models for several decades. Econometric models by design attempt to capture or represent simultaneously the data of interest and the ideas about how the modeled economy functions as reflected in that data. The primary task is one of identifying a set of parameters or constants that can be seen to characterize the economy being modeled. Such models are thought to represent a cause and effect relationship between two types of observable quantities. The effects are the endogenous variables being explained and the causes are the exogenous variables whose values are determined either by nature or by public policy autonomously but not necessarily independently of the model. Truly exogenous variables are variables determined by events beyond anyone’s control or by prior artificial constructs that by design are completely within the control of governmental policy makers (e.g., tax rates, subsidies, etc.). It is the posited fixed parameters that ultimately determine the effects of any changes in the causes. The hope has always been that econometric model builders could succeed in developing a model that would simulate accurately the workings of the economy, and with such a model, if the values of all its fixed parameters could be measured, we would then have an excellent and reliable tool for forming predictions and forecasts of the future state of the economy or of the effects of changes in government policies.