Median new home construction lot closing in on an acre

The median lot size of newly built homes in Greater Boston has risen to nearly an acre, roughly twice the median size of lots on which new local homes were built during the 1970s and 1980s, fueling concerns whether young and working-class families can afford to buy homes in Massachusetts.

Homes built on large lots potentially reduce the housing supply and put upward pressure on prices. While the local housing market has cooled recently, Massachusetts experienced the biggest housing price gains of any state from 2000 through 2003.

The study on lot sizes was conducted by the Massachusetts Institute of Technology Center for Real Estate and the Massachusetts Housing Partnership; its researchers said their findings contradict the quaint image of densely settled New England towns.

''This new data shows we are squandering land on large house lots" at a time when ''we are producing far less housing in Massachusetts than needed to sustain our state's economic growth," said Clark Ziegler, executive director of the Massachusetts Housing Partnership, a quasi-public state agency, in a statement.

Between 1998 and 2002, the estimated number of new single-family homes sold in Greater Boston was 30,387 and, collectively, those homes occupy just under 40,000 acres of land, an amount equivalent to the combined areas of Boston, Brookline, and Arlington, the study said.

The median lot size for new single-family homes sold during that period was .91 acres, the study found. The study cited US Census Bureau data to note that the median lot size for new homes built locally between 1990 and 1998 was .76 acres. Between 1970 and 1989, the median lot size of newly built homes was .46 acres, according to Census Bureau data.

''We knew that many towns had adopted large-lot zoning regulations, but we did not expect to see lot sizes this large, and the practice so widespread," said Henry Pollakowski, director of the Housing Affordability Initiative at the MIT Center for Real Estate.

The center analyzed sales data for 154 communities around Boston that was made available by the Warren Group, a Boston company that provides real estate information.

According to Pollakowski, no one has ever done such an analysis before.

''We were surprised that no one was keeping score on what was actually occurring," he said.

For national and historical comparisons, Pollakowski and his colleagues used American Housing Survey data collected by the US Census Bureau. The most recent year for which American Housing Survey data are available for the Boston metropolitan area is 1998.

For the 1970s, 1980s, and 1990s, the nationwide median for lot sizes for newly built homes held steady at a third of an acre, said Pollakowski, citing census data.

In 2003, the last year for which such figures are available, the nationwide median lot size for a newly built home was .43 acres, said a spokeswoman for the American Housing Survey.

Chris Reidy can be reached at reidy@globe.com.