This paper attempts to illustrate some future areas of quantitative historical research which have not yet received the attention we think they deserve. Our interest is primarily in aggregate economic systems. This emphasis is not motivated by a distaste for the analytical tools of microeconomics. On the contrary, a central premise of this paper is that macroeconomic models are ideally deduced from propositions about the behavior of individual decision-making units, and that they also critically depend on rules for the aggregation of such behavioral relationships. In fact, quantitative economic historians have long recognized the critical role played by aggregation rules in historical analysis. And, in the end, it will be the quantitative economic historian who will best be able to evaluate the efficacy of the employment of such rules in specified historical circumstances.