The origin of quantitative studies of population is most often traced to a single book: John Graunt's Natural and Political Observations Made upon the Bills of Mortality published in 1662. In this modest volume, Graunt, a London tradesman, argued that “Trade and Government may be made more certain and Regular” through the application of arithmetic, and that knowledge of “how many People there be of each Sex, State, Age, Religion, Trade, Rank, or Degree, &c.” provided a fair method “to balance Parties and Factions both in Church and State.” Writing in the immediate aftermath of the English Civil War, Graunt was keenly aware of the suffering caused by religious intolerance and economic turmoil. He also felt the widespread desire for order and stability after Charles II's ascension to the throne. Through quantification, Graunt sought to construct a new form of knowledge that could provide a trustworthy resource for reducing conflict, maintaining political equilibrium, and cultivating commercial prosperity.

Graunt's friend and patron William Petty fervently embraced the new project and coined a name for Graunt's method: political arithmetic. Petty shared Graunt's confidence in the certainty and regularity of mathematics.