Methods A total of five broad categories of population estimation methods have been identified. Every method has been organized in one of these categories: – Sampling methods – Site estimation methods – Counting methods – Remote estimation methods – Estimations using population data sets
Site estimation methods ’Guesstimates’ and community estimates Many organisations make very rough estimates (‘guesstimates’) based on visual assessments. This educated guess can only be done with some kind of visual picture of what, for example, 1,000 people looks like (UNICEF 2010).
Site estimation methods Key informants’ estimates (people and community leaders from the area, village elders, service providers, local authorities) can be important sources of information on population figures, family composition, household size, settlement patterns, and arrival and departure rates (CIEDRS 2003, UNICEF 2010).
Sampling methods Pre-crisis population size and location provides guidance on the areas to sample and the relative population sizes among villages (WFP 2007). If no detailed local maps are available it may be necessary to create them (e.g. displacement situations where refugee/IDP settlements are evolving) (CIEDRS 2003).
Sampling Method Quadrat method Obtain an aerial view or draw a map of the area of interest Measure the perimeter of the area. Create a scale outline of the area
Sampling Method Quadrat method Measure the total area by counting the number of full and partial quadrats. Select a random sample of quadrats. (Head count) Extrapolation: The average population density measured in the sample quadrats can be extrapolated directly to the entire area for an estimate of total population size Alternative: A population is never regularly distributed equally among a camp. Population density is higher in the middle of the camp where most facilities are initially located, while it is dispersed at the periphery
Sampling: T-square method. Select a random point (WFP 2009). A number of points (P), typically 60, are distributed across the area using computer software (either randomly or systematically) Measure the distance from this point to the nearest occupied house (WFP 2009): from each point (P) the distance (d1) to the nearest house is measured
Sampling: T-square method Go to this house, find the occupied house nearest to it, and measure the distance (d2) between the two houses Count the number of people living in the two houses and calculate the average Estimate the total area of the survey Calculate the average space occupied by these houses and its surroundings Calculate the total number of houses in the survey area by dividing the total area of the survey by the average space occupied by each house and its surroundings
Site estimation Participatory mapping Participatory mapping of the catchment area may be done by inviting a group of the affected population to sketch a map of the entire community on the ground or on a large paper. The catchment area is the geographical area from which all the people attending a particular health facility come (IFRC 2007).
Site estimation Focus group discussions A focus group discussion entails organizing and conducting a group discussion while ensuring that the group is ‘representative’ of all segments of the (IDP) community (e.g. women, men, community elders, adolescents, IDP leaders). This method is useful in obtaining additional data and should be triangulated with at least one other source, such as good baseline data or a quantitative source. Useful data elements that can be collected are perceived size of the (IDP) population and perceived sex and age breakdown (OCHA and IDMC 2008).
Site estimation Drive through / walk through A drive through involves driving through a disaster-affected area to assess the situation. Things to look for could include settlement patterns, quality of shelters, physical signs of distress (death, illness, conflict), household property (cooking facilities, livestock) and community resources (clinics, schools, wells) (CIEDRS 2003).
Site estimation Water usage data Relies upon the assumption that the population number in a camp can be estimated by the average amount of water used by each individual. Immunization /Food delivery data
Site estimation Mobile crowd estimation Estimates the size of a mobile population in which people may join or leave the march at various points. The number of participants, N, in the demonstration is defined to be the number of people who entered the demonstration route.
Satellite imagery / Remote sensing Satellite images can allow for detailed camp area estimates during an emergency or crisis, but can also provide baseline data for an area which is susceptible to a shock.