This isn't the wealthiest metropolitan region in America, nor the fastest-growing.

Our national ranking in terms of income, education, culture and technological altitude is debatable.

But there's one area in which the Philadelphia region is evidently way out in front of the pack, with only a handful of other metros for company:

We've got some of the tightest zoning in the land.

According to a new Wharton School study, the cities, towns and boroughs in this region regulate development more strictly, on average, than the vast majority of American communities.

Builders and developers here must spend more time, obtain more approvals, and jump through more bureaucratic hoops than almost anywhere else in the country, say the study's authors, Wharton professors Joseph Gyourko and Anita Summers.

Their survey found that only around Boston and Providence, R.I., are zoning regulations more stringent, on average, than they are here. Among other major metropolitan areas, only San Francisco and Seattle are in a class with Philadelphia.

The findings stem from a multiyear project by Wharton's real estate division, which surveyed zoning practices in more than 2,600 towns and cities across the country.

What they found in the Philadelphia region may not surprise anyone who has ever followed a local zoning case.

The process is typically long, convoluted and expensive, with multiple approvals and layers of appeal.

And that's true even if the project conforms to existing zoning rules.

The evidence: The average time it takes for a local board in this area to review a land-use case is double the national average, Summers said.

Why are the rules here so strict? That's a tougher question. Motivations overlap: A community's desire to conserve open space can be hard to separate from racial exclusion, snobbism or simply the pursuit of higher real estate values.

"We don't know to what extent the Gladwynes of the area are protecting their air and water vs. the value of their homes. What we know is they vote for more regulation. That's what they want," Summers said.

Not that regulation is uniform across the region. There are big differences in how aggressively local communities seek to control development.

Some of those differences might surprise you, moreover. For example, it's not the more built-up communities that have the tightest zoning rules - quite the opposite.

In general, the more dense the area, the less rigorous the zoning.

That includes Philadelphia proper, which is studying an overhaul of its zoning code. By Wharton's yardstick, the city is more developer-friendly than most of its suburbs.

"Central cities in general are less regulated by our measure, than the suburbs," Gyourko said. "In many suburbs, you can't get anything through. They just don't want it."

That not-wanted-here attitude has a cost. Regulation increases development costs, making it harder to build - or find - affordable housing.

"Individual communities have an incentive to restrict development," Gyourko said. "When you add up all those restrictions, they can really make housing expensive in a metro area."

The researchers also strongly suspect a link between tight land-use restrictions and regional economic growth.

It's a matter of basic supply and demand, Gyourko said. In Boston or San Francisco, tight land-use regulations coincided with surging demand, as those regions took off during the tech boom of the 1990s. The result: housing prices that soared into the stratosphere.

Philadelphia real estate markets were generally much tamer, but that doesn't mean land-use regulations aren't having an effect, Gyourko said.

Rather than pushing up prices, regulation here could be restraining regional growth. Further studies might prove that's the case, he said.

"The data are highly suggestive," Gyourko said. "Do we have a smoking gun there? No. But it's true."