On Estimating a De Facto Population and Its Components

This paper deals with estimating a population that is largely defined by the fact that its size, composition, and distribution are not readily accessible from census data in the U.S. and the other countries that use the De Jure concept of population. The population in question is based on the De Facto concept, which involves the estimation of people where they are found rather than where they usually reside. In a country where the national statistical office uses the De Jure concept, estimating the De Facto population as well as its components is an important, but not easy task. It is important because of the many uses for estimates of the De Facto population; it is difficult because the data that can be used to estimate a De Facto population are skimpy. In an effort to develop this field of population estimation more fully we provide an equation to define the De Facto population as well as an example of its use. We describe and discuss each of the components of this equation and also provide examples of estimates of its direct components and an implied component ¨C the daytime population. Although we view a population impacted by a disaster as distinct from a De Facto population, we include a discussion of it here since many of the methods used to estimate a De Facto population are applicable.