Estimating Households by Household Size Using the Poisson Distribution

Beth Jarosz, San Diego Association of Governments (SANDAG)

This research documents a statistical technique for estimating the distribution of households by household size using a modified application of the Poisson distribution: P=(M^n*e^-M)/n! where: n = household size - 1, M = mean size - 1, and P = the probability of case n. This technique is valuable to demographers as it provides a tool for addressing discrepancies found between household size and household population data reported in the American Community Survey. This article puts forth two key advancements over prior published work: (1) an entirely new and simplified method for applying the distribution, (2) evidence of the reliability of the technique for estimating household size distributions in small geographic areas (e.g. census tracts). Tests on U.S. Census data (1990-2010) show that the model is suitable for use in estimating the distribution of households by household size at the state, county, and census tract level.