Household Dynamics and Per Capita Environmental Impact
Brant Liddle, Max Plank Institute for Demographic Research, Germany
Current contact information:
5604 York Lane
Bethesda, MD 20814
USA
Phone: 1-301-652-1755
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btliddle@alum.mit.edu
ABSTRACT
One of the important new trends in population-environment studies has been the consideration of
households as the unit of analysis. Focusing on households is important because much environmental
significant activity is “consumed” at the household level, e.g., personal transport and residential energy use.
Furthermore, in many countries in which population has remained constant or declined, the number of
households has increased and household composition (e.g., number of members, age and gender of head)
has changed substantially. This paper examines US household data (from the Residential Energy Use
Consumption Survey) and employs standard techniques from the demographic literature to determine to
what extent compositional changes in the nature of households can explain changes in per capita
environmental impact (e.g., miles driven and residential energy use) both over time and across regions.
A change in a weighted average (e.g., per capita environmental impact) can be decomposed into the
average change (in demand for the activity) and the covariance between the variable of interest and the
intensity of change of the weighting function (the growth rate of relevant populations). For example, the
demand for personal transport has increased at the same time households have become smaller. Since there
are economies of scale for mobility at the household level, changes in per capita miles driven can result
from both of the above trends. The early result from these decompositions is that changes in personal
transport demand are more important than compositional changes, however, during some periods and in
some regions the compositional change component is significant.