Water drips from a tap as people sit in a slum south of Cairo, Egypt. Amr Abdallah Dalsh/Reuters

Even in countries that have made a lot of progress, measuring sustainable development at the neighborhood level exposes the inequality within cities.

With the world’s population growing fast, and at least two-thirds of all people projected to live in urban areas by 2050, there’s more attention than ever on how to handle this growth in sustainable ways. Just two years ago, the United Nations adopted an ambitious set of 17 sustainable development goals with the intention of meeting them worldwide in just 15 years. But measuring and quantifying sustainable development has never been easy. And since it’s done at the national level, the numbers often fail to reflect the inequality found within each city.

So in a new paper, a group of researchers created a new index to measure progress at all scales, including at the neighborhood level. “It's by taking this microscope and getting closer to people's actual experience that you then see inequality,” says Luis Bettencourt, who studies urbanization at the Santa Fe Institute.

Progress is rarely consistent across a city—much less across an entire nation. So just because a nation scores high on providing basic services, it may not mean those services are distributed equally to all pockets of its cities. That becomes a problem when local and national leaders need to figure out what policies to develop and where to target them. “When we're not looking at the fine-scale levels within a city, you miss a lot of the [inequality],” says Christa Brelsford, who led the study while she was a postdoctoral fellow at the Institute. (She’s now a fellow at Oak Ridge National Laboratory).

Their alternative, simpler method for measuring sustainability focuses on the kind of fine-grain data that is available, or can be collected, to assign each neighborhood four scores, on an index from zero to one, for how many people have access to electricity, running water, improved sanitation, and permanent housing. These were the dimensions that Brelsford says most closely match the U.N.'s own index for sustainable development. “We wanted it to be as comparable as possible to the indices that are already in use,” she tells CityLab. Using the U.N.’s own criteria, for example, a neighborhood would score zero if nobody had access to a water source within 200 meters of their house, while a score of one means everyone in that neighborhood has access.

Those numbers are then combined to give each neighborhood a final score, and when mapped, they show how sustainable development differs from place to place. And since the index looks at what proportion of the population has access to certain services, it can also measure progress at the city, regional, and even national levels to see how inequality plays out at different scales.

When the researchers apply their index at different scales to South Africa and Brazil—chosen, Bettencourt says, because they have recent and detailed data on their neighborhoods—they found some general patterns. People in the largest cities tend to have more access to basic services overall. When they zoomed into the neighborhood level, though, the researchers found that cities also tend to have some of the highest levels of inequality when it comes to the distribution of those services.

Brelsford and Bettencourt’s sustainable development index has its roots in the Human Development Index, developed in 1990 by the late economist Mahbub ul Haq as a more human-centric approach to measuring the wealth of a nation. Before that, a nation’s progress was largely based on its economic growth, which Bettencourt says doesn’t tell the whole story.

Instead, the human development index focuses on human capabilities, measured through income, education, and life span. “The sense is that the most important thing to look at is not necessarily about different incomes, but what they can do with the services and incomes that they have,” Bettencourt says. “Are they essentially free to pursue a life of opportunity, or are they so tied down by satisfying everyday needs that they have no chance?”

The human development index emphasized that all three dimensions must exist to ensure a population’s wellbeing—something that the researchers incorporated into their own index. By their definition, sustainable development means people need to have access to all services, not just a few.
Suppose a neighborhood scores zero on housing but one on water access. “Should the index say it scores in the middle, or should it score low?” Bettencourt says, adding that while other indices adds individual scores together, their method propose that they be multiplied instead. “The point is that one thing should not substitute the other, and when you multiply, you basically emphasize that having nothing [in one category] is totally disabling.”

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