In most of the nation, household sizes are getting smaller, but home sizes, according to the number of bedrooms, continue to grow, according to the most recent analysis of the U.S. Census Bureau's American Community Survey. Twenty percent of occupied homes had four or more bedrooms in 2005, compared to 17.7 percent of homes in 2000.

Homes are ballooning. In America, bigger is better because size equates to prosperity, the foundation of the American dream.

In 2005, the average floor area in a newly built home reached an all-time high of 2,434 square feet -- up from an average 2,349 square feet in 2004 and just 1,645 square feet in 1975. In 1973, two-thirds of new homes were one-story. By the 1980s, home sizes had risen nearly 25 percent, despite the high energy costs of running a larger home. In 2006, the majority of homes were two-story to accommodate larger floorplans on smaller lot sizes.

Like car buyers, homebuyers took advantage of soft energy prices throughout the late 1980s, 1990s and early oughts to build bigger, higher volume homes. As neighborhoods sprawled from urban centers, returns from the stock market dwindled, and low interest rates made buying and building bigger more attractive, consumers demanded even more space, until home sizes reached an all-time high by the mid-oughts. Long commutes combined with cheaper consumer goods to create demand for media rooms, home offices, exercise rooms, spa baths, and other specialty spaces.

Meanwhile, the U.S. Census showed that households were shrinking, from 3.14 people in 1970 to 2.58 people in 2002.

In 2005, Utah had the most homes with four or more bedrooms (four out of 10 homes or 39.2 percent). Maryland ranked second at 28 percent. Colorado (26.2), Delaware (25.8), Minnesota (26.2), North Dakota (26.1) and Virginia (26.5) also have a large percentage of bigger homes.

Among counties with populations of 65,000 or more (the threshold for 2005 American Community Survey data), Davis County, Utah (49.4 percent); Fayette County, Ga. (45.5); Forsyth County, Ga. (48.5); Loudon County, Va. (44.6); Stafford County, Va. (43.8); and Utah County, Utah (45.7) had the highest percentage of homes with four or more bedrooms.

Cities with populations of 65,000 or more that stand out in this category include Allen, Texas (52.0); Centennial, Colo. (52.5); Naperville, Ill. (53.0); Sandy, Utah (63.8 percent); and Sugar Land, Texas (55.3).

But will the trend of bigger homes last?

Several changes in demographics and economic indicators that fueled larger cars and larger homes are happening:

• Median home values have jumped approximately 40 percent between 1990 to 2005 to about $167,500.

• Baby boomers, the largest population segment at 78 million in 2005, began turning 60 in 2006. As they become empty nesters, many tend to downsize.

• The cost of land and materials, as well as operating costs, may cause many homebuyers to think twice about buying a home larger than they need now and in the future.

• Rising gas prices and a growing traffic problems from suburbs where the majority of larger homes are being built may cause some homebuyers to rethink the tradeoff between owning a big house and a long commute.

The National Association of Home Builders is reporting that home sizes are beginning to moderate and are down slightly from the record high reached in 2005. In fact, in its 2010 projection, the NAHB anticipates that home sizes won't be larger than they are now. What homebuyers will demand instead of size is more flexibility in floorplans so they can configure their interiors to suit their individual needs.

The American Institute of Architects Home Design Trends Survey also suggests a counter trend of moderation, primarily due to affordability issues and energy costs. In 2007 fewer homeowners wanted increases in square footage and volume, while more homeowners wanted single-floor plans. Because of the cost of "footprints" or foundations and land, single-story homes built in the future will be smaller than two-story homes are now.