John Graunt, a largely self-educated London draper, can plausibly be regarded as the founding father of demography, epidemiology and vital statistics. In his only publication, based on a pioneering analysis of the London Bills of Mortality, he replaced guesswork with reasoned estimates of population sizes and the first accurate information on male:female ratios. He quantified the extent of immigration from countryside to city and his demonstration of the 'dying out' of a cohort paved the way for life table analysis. His comparison of London data with rural data provided the first recognition of the 'urban penalty'. His use of the first known tabular aggregates of health data clarified distinctions between acute diseases, which were often epidemic, and chronic illnesses which were often endemic. He quantified the high infant mortality and attempted the calculation of a case fatality rate during an epidemic of fever. He was the first to document the phenomenon of 'excess deaths' during epidemics. He provided a template for numerical analysis of demographic and health data and initiated the concepts of statistical association, statistical inference and population sampling. By making a novel concept intelligible to a broad audience he influenced the thinking of doctors, demographers and mathematicians.
Keywords: William Petty; bills of mortality; demography; epidemiology; john Graunt; plague; political arithmetic; vital statistics.