Major theoretical advances in understanding the operating forces of society have not led to corresponding improvement in techniques of forecasting. Ranging across the major socioeconomic theories bearing on demographic trends - from demographic transition theory to human capital theory - this paper asks whether there are scientific results neglected by forecasters that would help population forecasting and, if not, what it is in the nature of scholarship that makes it unusable for this purpose. The static and conditional nature of most theory, the presence of confounding factors that swamp the postulated effect, and uncertainty of timing are among the major limitations in application of theoretical insights to forecasting. Pending discovery...