Statistics on Sprawl Meaningless if They Oversimplify

"Sprawl index" oversimplifies a complex process

Every political movement needs a statistic, and nowhere is this more true than in the so-called Smart Growth movement.

The statistic du jour is something called a “sprawl index,” which supposedly identifies the real culprits in sprawl – states and cities developing land at a faster rate than their population growth. The sprawl index got a big boost when the Brookings Institution recently released a study claiming that developed land grew almost three times faster than the population in America’s metropolitan areas from 1982 to 1997.

Like most politically driven statistical measures, however, the index oversimplifies a complex process. Embracing it implies that population and land development growth rates should be the same. This is an absurd standard; taken literally, it would suspend the dreams of millions of homebuyers and seriously compromise the quality of life for millions of families.

Let’s jump back 50 years to see why. This is urban America right after World War II, before modern suburbs, the interstate highway system and the creation of mass-produced affordable housing communities. Many, if not most, people live in apartments or row houses in densely populated inner cities.

How dense? A four-floor apartment building, housing families with an average of two kids, two families per floor, would generate a housing density of about 134,000 people per square mile. While some blocks achieve these densities, most cities are less dense on a citywide basis because the overall density is diluted by land uses that don’t house people – roads, office buildings, schools, parks, etc.

In contrast, a contemporary suburban subdivision, populated with similar families with houses on lots of a half-acre would generate a residential housing density of about 5,000 per square mile (often less than 2,000 once the other land uses are added in).

Let’s say our apartment families, whose parents toil away on the local assembly line, scrape together enough money to rent a new row house – an attached single-family home fronting the street with a small yard in the back. Since this is a growing city, these families are replaced by new households and the population doubles.

But, the move means land development outstrips population growth by three to one because the homes are next to each other, not stacked on top of each other in one building.

Is this rampant, uncontrolled sprawl that must be stopped? If the sprawl index is to be taken seriously, it is. The only way population growth could match land development is if these families moved into a new apartment building at the same density – no yard, no additional living space and no garage.

The index, it turns out, is a crude measure that obscures more than it illuminates. Cities, like economies, evolve, and where a city takes off economically has an impact on its architecture, design and housing patterns.

Take two cities, close geographically, but worlds apart in economic legacy and land use are Cleveland and Columbus, Ohio. Industrial Cleveland has seen its population density fall by more than a third from its post-World War II high of almost 10,000 people per square mile. While the city is experiencing a modest housing renaissance, new housing is primarily suburban. In fact, new housing in the city’s inner-city Hough neighborhood is virtually indistinguishable architecturally from similar homes in suburban settings.

Meanwhile, a couple hours south, population densities will increase by at least 9 percent in half of Columbus’ neighborhoods. With fewer than 2,000 people per square mile, however, Columbus’ citywide population density is about one-third of Cleveland’s and consistent with suburban lifestyles.

A sprawl index would give Columbus high marks because its density will increase and Cleveland low marks because its population density will fall. Yet, the key to success for both cities is providing housing that fits the modern household – larger homes with more luxury characteristics, automobile accessibility and a small yard.

In a nation where only 5 percent of the land is developed, and only one state (New Jersey) has developed land exceeding one-third of its total surface area, statistical measures such as a sprawl index are meaningless. Ultimately, they serve little purpose other than to conjure up unsubstantiated fears about land use and dismiss immediately accessible land as a desirable characteristic of housing.

More importantly, perhaps, they provide almost no guidance to local policy-makers and elected officials struggling with the real problems of growth – rising traffic congestion, deteriorating environmental quality and rising infrastructure costs. The challenge for elected officials and citizens is to come up with specific solutions for specific problems, not use meaningless statistics to adopt broadbrush approaches to land use that run counter to what people really want.

Samuel Staley is director of urban and land use policy at Reason Foundation and co-editor of the book “Smarter Growth: Market-Based Strategies for Land-Use Planning in the 21st Century.”