In the case of the earthquake, the victims themselves were unaskable, so polling their families, friends and neighbors was the only way to estimate their numbers. Bernard realized, however, that these techniques might also work well to estimate certain groups of living victims, especially those who have experienced events or suffer from problems that they'd be unlikely to talk about openly, such as rape, HIV, or homelessness, the three topics his work now focuses on. Official counts of people in these categories, culled from hospital and police reports, are usually thought to be low, since the victims often too embarrassed or frightened to admit their condition. Bernard hopes to overcome this hurdle by surveying people about others instead of themselves. Most people are willing to provide information about members of their social circle, as long such information is completely anonymous.
Some people know more people than others, and socio-economics also come into play.
In the case of the earthquake, for example, wealthier respondents would probably have known fewer people who lived in the kind of housing vulnerable to destruction by natural disasters, while poorer respondents may have known many. They ask each person surveyed questions not only about these three target groups, but also about 29 other groups whose population sizes are already known, such as Diner's Club card carriers, men named David and diabetics. Once this network size is established, they can estimate the size of the populations whose sizes are unknown. Their results are promising. There are many potential applications of their research, but Bernard stresses one in particular.