"One could build models designed just for predicting the future, and some scholars do. If so, one might include, for example, presidential approval as a forecasting variable. That variable 'predicts' very well. But it is theoretically uninteresting. The variables we want to test, like the economic variables, will also affect presidential approval, and so including it hinders our ability to estimate the effect of the variables we care about. Such a model might be great at predicting the future, but it’s lousy for social science." Hans Noel delivers an excellent lesson on the issue of predicting versus modeling.