No Light Rail in Vancouver!

Home Grand Jury Findings Rail Supporters Europe Rail Neighborhood The Plan Cars The Bridge Publications No Tolls!
Light rail costs too much, does too little

I have a lot of questions about the validity of this survey data, some of which I described in a Vanishing Automobile update. But for the sake of argument, let’s say the survey data are accurate.

In 2003, Smart Growth America and the Surface Transportation Policy Project announced that they had proven that “sprawling development has a hand in America’s obesity crisis.” They used the CDC data to compare obesity rates in suburbs vs. cities and concluded that the suburbs were fatter.

Curiously, the CDC data do not identify whether someone lives in a suburb or a city. But that is not enough to stop junk scientists. The CDC data do identify counties, so the smart-growth groups simply compared county rates of obesity with a “sprawl index” that the calculated for each county.

A second problem with the study is that America has been suburbanizing for more than a century, and the most rapid suburbanization took place in the 1950s and 1960s. How could this suburbanization cause an obesity crisis in the 1990s?

But an even more important problem is that the numbers associating sprawl and obesity are very weak. As Wendell Cox points out, the data show that residents of dense Boston weigh just 1.7 pounds more than Boston suburbanites, while those of denser Chicago weigh just 1.4 pounds more than that city’s least dense suburbs. These tiny difference are much less than differences found between people of varying incomes and educations, and certainly do not prove that suburbs have made Americans fat.

In order to give their study more credibility, the smart-growth advocates published a version of it in a peer-reviewed medical journal. To get into the journal, however, they had to seriously weaken their claims. Sprawl “had small but significant associations” with obesity, says the journal article. In the popular mind, “significant” means “having a major effect,” but in statistics all it means is “not random.” So the article admits the correlation between sprawl and obesity is not random, and — unlike the press release — the article nowhere claims that one caused the other.

Instead of sprawl causing obesity, two recent studies from Oregon and Canada agreed that the reverse is true: obesity causes sprawl. That is, obese people choose to live in sprawling communities because such neighborhoods are better suited for their needs. If this is true, then there is no justification for Smart Growth America’s call to rebuild the suburbs.

Another flawed study compared sprawl and chronic diseases. Like the obesity study, this one was based on a telephone survey. Like the obesity study, the survey did not distinguish between suburbs and cities, so the junk scientists who did the study compared low-density with high-density urban areas. Like the obesity study, the correlations were weak: sprawling Atlanta and Minneapolis-St. Paul both had lower incidences of health problems than compact San Francisco and New York. Yet the people who did the study were quick to blame the suburbs for various health problems.

Instead of relying on a crude telephone survey, we could take an objective look at actual health records for people living in cities, suburbs, and rural areas. One study that did so found that actual mortality rates are significantly higher in urban areas than in rural areas. Suburban rates were only slightly higher than rural rates. So much for suburbs being unhealthy.

Both the obesity and chronic disease studies have all the hallmarks of junk science. They used data bases that did not really measure what they were trying to measure (suburbs vs. cities). They found very weak correlations. They claimed that these correlations proved causation. And the groups that did these studies continue to promote the idea that sprawl is unhealthy even though more recent studies have proven them wrong.

Unfortunately, like the General Motors conspiracy myth, it appears that the junk scientists who promoted the sprawl-kills myth were successful enough that it will take a long time for this myth to die.

13

Trackback  •  Posted in Regional planning, Why Planning Fails  

Junk Science Week: #3 - Obesity & Health

Feb 21

2007

Everyone knows that the suburbs made us fat. How do we know this? Because some junk scientists at some pro-planning advocacy groups put out a press release that claimed they had proven that suburbanites were fatter than city dwellers.

In fact, their research proved no such thing. But they did not hesitate to argue that their “proof” showed that America needs “to to invest in making America’s neighborhoods appealing and safe places to walk and bicycle,” which — to planners’ way of thinking — means rebuilding suburbs at higher densities.

Each year for nearly two decades, state public health agencies have conducted telephone surveys of some 200,000 people asking such nosy question as how tall they are and how much they weigh. Ominously titled the Behavioral Risk Factor Surveillance System, this survey is sponsored by the Centers for Disease Control (CDC). Based on this survey, the CDC says that American obesity rates have nearly doubled since 1990.

Reprinted from The Antiplanner