Rapid assessment of population size by area sampling in disaster situations

In the initial phase of a complex emergency, an immediate population size a ssessment method, based on area sampling, is vital to provide relief worker s with a rapid population estimate in refugee camps. In the past decade, th e method has been progressively improved, six examples are presented in thi s paper and questions raised about its statistical validity as well as impo rtant issues for further research. There are two stages. The first is to map the camp by registering all of it s coordinates. In the second stage, the total camp population is estimated by counting the population living in a limited number of square blocks of k nown surface area, and by extrapolating average population calculated per b lock to the total camp surface. In six camps selected in Asia and Africa, between 1992 and 1994, population figures were estimated within one to two days. After measuring all externa l limits, surfaces were calculated and ranged between 121,300 and 2, 770, 0 00 square metres. ln five camps, the mean average population per square was obtained using blocks 25 by 25 metres (625m(2)) and for another camp with blocks 100 by 100m(2). In three camps, different population density zones w ere defined Total camp populations obtained were 16,800 to 113,600. Although this method is a valuable public health tool in emergency situatio ns, it has several limitations. Issues related to population density and nu mber and size of blocks to be selected require further research for the met hod to be better validated.