Evaluating the human condition occurs in many disciplines - for example, epidemiology, sociology, political sciences, criminology, and market research. Despite advances in these fields progress has been sluggish compared with that in the “hard” sciences. A primary force for rapid developments in these sciences has been the discovery and use of new technologies (for example, the polymerase chain reaction, electron microscopy, carbon-14 dating), which increase the precision of measurement and reduce costs, resulting in a rapid accumulation of knowledge.1,2 Human population science has society as its laboratory and “counting humans” as its basis. Counting techniques, however, have changed little this century. The use of capture-recapture techniques could bring about a paradigm shift in how counting is done in all the disciplines that assess human populations.

Historically, the main approach to evaluating human populations has been to find the members of a community with a characteristic of interest and count them - for example, researchers have counted people with a particular disease (epidemiology), income level (economics), and party affiliation (political science). This approach is rooted in the belief that one needs to count and classify everyone to know about them. Complete enumeration, though, is costly and inefficient. Alternatives such as sampling a small group and extrapolating the results to a region or nation have been developed. These techniques may, however, be slow, costly, limited, and “foreign” to the people who need the data for policy - for example, governments.

Governments typically cannot …