The result often is urban sprawl. As a household shrinks and as more households form, the economy of scale is lost. Each household requires resources to construct it and takes up space. It requires fuel to heat and cool it. A refrigerator uses roughly the same amount of energy whether it belongs to a family of four or a family of two. Increased energy consumption also increases the emission of greenhouse gases, which is believed to contribute to global warming.
"In larger households, the efficiency of resource consumption will be a lot higher because more people share things," Liu said. "Usually, many people will share living space and other resources. This is true in all countries."
Moreover, households may be shrinking in size, but growing in terms of square footage. Fewer people tend to live in more space, thus further using resources.
For example, in Indian River County of Florida, the average area of a one-story single-family house increased 33 percent in the last three decades, from an average of about 1,800 square feet in houses built before 1970 to an average of roughly 2,400 square feet built between 1970 and 2000.
The household project grew from Liu's years of research on how humans interact with fragile wildlife habitat in China's Sichuan Province. There, villagers compete for resources with the beloved, and endangered, giant pandas.
"In China and many other countries around the world, incentives created to help the environment are based on households," Liu said. "These incentives have good intentions, but they also encourage households to break into smaller households.
"The issue of the number of households and their impact on the environment basically has been ignored. It was eve
Contact: Jack Liu
Michigan State University