Long-term dynamics of household size and their environmental implications

Little is known about the environmental implications of long-term historical trends in household size. This paper presents the first historical assessment of global shifts in average household size based on a variety of datasets covering the period 1600–2000. Findings reveal that developed nations reached a threshold in 1893 when average household size began to drop rapidly from approximately 5.0 to 2.5. A similar threshold was reached in developing nations in 1987. With the notable exceptions of Ireland, and England and Wales in the early 1800s, and India and the Seychelles in the late 1900s, the number of households grew faster than population size in every country and every time period. These findings suggest accommodating housing may continue to pose one of the greatest environmental challenges of the twenty-first century because the impacts of increased housing present a threat to sustainability even when population growth slows. Future research addressing environmental impacts of declining household size could use an adapted IPAT model, I = PHoG: where environmental impact (I) = population × personal goods (P) + households × household goods (HoG).