Annette L. Adams
The capture-recapture method is a technique for estimating the size of a population that cannot be directly measured in its entirety. It is derived from ecological research methods. To take a census of a group of animals (e.g., the population of fish in a pond), researchers capture a subset of animals, mark or tag them in some way, release them, then capture another sample (recapture). Some of the animals from the first sample will reappear in the second sample as well; some animals will appear only in one of the two captures. From this information, the size of the whole population can be estimated. Capture-recapture methods have been adapted by epidemiologists for use in the surveillance of and identification of human illnesses. Routine surveillance methods are likely to fail to identify every affected person. Capture-recapture methods can be used ...