BOULDER, Colo. — Single-family homes dominate the residential building stock in the United States. However, according to a new report from Pike Research, a part of Navigant’s Energy Practice, the number of single-family homes is now decreasing. By 2021, the report says, the total area of single-family homes in the United States will have shrunk by nearly 4 billion square feet, contracting at a negative compound annual growth rate (CAGR) of 0.2 percent.

Single-family housing accounts for more than 80 percent of total residential space. Over the last 60 years, the number of single-family homes in the United States has grown and the size of each home has increased, growing by about 40 percent between 1975 and 2010, according to the U.S. Census Bureau.

“For the first time since World War II, the United States is experiencing increased levels of urbanization,” said senior research analyst Eric Bloom. “As more people move into cities, they tend to occupy apartments, condominiums, and other attached multi-unit housing types. By 2021, over one-fourth of the residential stock of the United States will be in multi-unit residential buildings.”