By Alison Rice. It's a perennial topic in the home building industry. "Since I got here in 1984, builders have been talking about how they're spending more on land," says Michael Carliner, an economist at the NAHB. "But the ones that aren't spending more aren't talking."

It turns out that those silent builders may be the majority. According to researchers, land costs have remained fairly stable and affordable in most of the country. In 2000, the average lot cost represented 20.4 percent of a home's sales price--just as it did in 1996, says Carliner, who published his findings in the January 2002 issue of Housing Economics.

What gives? Lot size. Builders are offering larger homes on smaller lots--a median house of 2,080 square feet on an 8,750-square-foot lot in 2000. Such decisions have kept housing costs reasonable despite increases in the per acre cost of land.

But that isn't always an option, even when high land prices might suggest higher densities. "A builder won't put a $50,000 house on a $100,000 lot," Carliner says. "When the price goes up, he feels like the only product he can build is luxury."

That leaves land-use regulations as the obstacle to housing affordability.

That's the assertion of researchers Edward L. Glaeser and Joseph Gyourko, of Harvard University and the University of Pennsylvania, respectively, who recently.

According to the researchers, housing prices are affordable for most of the country. The average home costs about $127,500 to build, very close to the 2000 U.S. Census' median home value of $120,000.

Of course, such numbers don't apply in California, Seattle, or the Northeast. Demand isn't the issue, Gyourko says. Regulations are.

"If land-use regulations are binding, you have huge price effects," he says. "If you don't have binding constraints, houses are valued at what it costs to build them."

As a result, Gyourko and Glaeser suggest that housing affordability isn't a national issue, but a regional one.

Others say it's not quite so simple. While restrictive zoning certainly affects housing prices, building at the urban fringe (or the Midwest), where regulations and costs are lower, isn't always the answer. "It depends on where you're looking for affordable housing," says John McIlwain of the Urban Land Institute. Prices may be cheaper in the distant suburbs, but the jobs may be closer in.

And, unfortunately for builders, land-use regulations are popping up all over. "I'm not sure there's a community we do business with in the country that doesn't have this issue," says George Seagraves, president of D.R. Horton's northeast region.