November 21, 2012
Vol: 19 No: 47

News

Study shines new light on King County’s ‘food deserts’

By Amy Roe , Editor

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In the 1990s, social scientists in the United Kingdom began using the term “food desert” to describe communities where people had a hard time getting access to fresh, healthy food.

Food deserts have since become a hot topic among public health officials in the U.S.. And, according to a map created by the USDA, there are few food deserts in our state.

Really?

“You look at the food desert [map] in Washington state, you have to laugh a little bit,” said Anne Vernez Moudon, professor of urban design and planning at the University of Washington.

“The methods to identify food deserts were too simplistic,” she said, “and therefore, sort of biased.”

To get a more accurate picture of food deserts in King County, Vernez Moudon, her colleagues Philip M. Hurvitz, Adam Drewnowski and Jared Ulmer of the UW and Junfeng Jiao of Ball State University included factors that had been omitted in previous studies.

They considered the time it takes to get to a store instead of the distance and what people paid for groceries once they got there. Rather than identifying food deserts using aggregated data from zip codes or census tracts, as previous researchers have done, they studied smaller, more specific census blocks, each the rough equivalent of an urban city block.

What they discovered was that for those who lack access to a vehicle, food deserts are actually quite common in King County.

The study, published earlier this year in the American Journal of Public Health, is called “How to Identify Food Deserts: Measuring Physical and Economic Access to Supermarkets in King County, Washington.”


Minutes versus miles

About 5 to 8 percent of the population in King County lacks access to a car, so instead of looking at the distance of a low-income area from a supermarket, as the USDA does, Vernez Moudon and her co-authors looked at a more meaningful metric: time. Driving two miles instead of one doesn’t make much difference, but it can be pivotal for those walking or using transit.

The co-authors found that nearly all of the vulnerable populations in King County lived within a 10-minute drive or bus ride of a low- or medium-cost supermarket. But take away the vehicle or transit access, and things change dramatically.

On foot, at most only 34 percent of the vulnerable populations could reach a supermarket at all, and only 3 percent could reach a low-cost store.

To use time, rather than distance, as a frame of reference, “You have to have more data,” Vernez Moudon said, “but it’s not impossible.”

It’s revealing. Access to a car was the best guarantee that the majority of the vulnerable populations would reach any supermarket within 10 minutes, the threshold for accessibility chosen by the researchers.


Types of stores

Earlier studies of food deserts did not make distinctions among supermarkets. Since people are price-sensitive when shopping for food, Vernez Moudon and her colleagues accounted for the types of supermarkets available.

They used a standard index of common items, called a market basket, to gauge the price of different supermarkets, dividing the stores into low, medium and high cost categories.

What they found may not surprise anyone who has ever lived in South King County. When supermarket access was defined as pedestrian access to a low-cost supermarket, the number of areas defined as a food desert dramatically increased throughout the King County map.


New directions

Vernez Moudon said she hopes public health officials will use this information to lobby government regulators to create incentives to developers to place affordable grocery stores in neighborhoods that lack them.

As they go about creating walkable neighborhoods, communities should also demand walkable grocery stores.

For example, Vernez-Moudon said securing a supermarket is a priority for the planned retail space that will be included in the redevelopment of Yesler Terrace public housing.

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