Paving Paradise

It’s just a guess, but I doubt concrete would rank high on a list of the world’s most loved materials. From Belgrade to Brixton, the antiseptic, brutalist tower blocks of wannabe Le Corbusiers have become eyesores — vertical slums infested with graffiti and gangs. Twenty-lane highways in Houston are not generally considered a thing of beauty to anyone but transportation engineers. And for each megawatt of electricity produced by China’s enormous Three Gorges Dam — the world’s largest concrete construction project — roughly 77 people were booted from their homes. But what if, at the risk of infuriating Joni Mitchell, the path to paradise really is paving a parking lot?

If you’ve ever traveled, say, to a remote village in Swaziland and then returned years later to find that the charming dirt road is now paved over, there’s a good chance you’ll feel a bit of nostalgia for the way things were. Don’t. There’s also a good chance that the people there now are a lot healthier, happier, and wealthier than they were the last time you visited. All thanks to a little concrete.

Consider what it’s like to live in a mud-floor house, as nearly 80 percent of rural Kenyans, and hundreds of millions of people worldwide, do. It is effectively impossible to clean such floors, which is a big reason that more than half a billion people worldwide are infected with hookworm, according to scientist Peter Hotez of the Sabin Vaccine Institute. Walking barefoot on soil floors is one of the most common ways to get hookworm disease — a parasitic infection in which larvae burrow through skin, lodging in the gastrointestinal tract, living off the host, and making children very sick. Kids with hookworm are less likely to go to school and become healthy adults. The economic impact can be considerable: University of Chicago economist Hoyt Bleakley estimates that children infected with hookworm in the American South in the early 1900s went on to earn 43 percent less in wages as adults.

There are cheap ways to combat such nasty diseases. A package of drugs covering hookworm and a range of parasitic infections costs as little as 50 cents per person per year. Reinfection, however, is frequent, and improper use of the medicine can create drug-resistant strains. What works best? Not drugs, but pavement; it typically costs just a few dollars per cubic foot and can last a lifetime.

Here’s proof: Starting in 2000, a program in Mexico’s Coahuila state called "Piso Firme" (Firm Floor) offered up to $150 per home in mixed concrete, delivered directly to families who used it to cover their dirt floors. Scholar Paul Gertler evaluated the impact: Kids in houses that moved from all-dirt to all-concrete floors saw parasitic infestation rates drop 78 percent; the number of children who had diarrhea in any given month dropped by half; anemia fell more than four-fifths; and scores on cognitive tests went up by more than a third. (Perhaps unsurprisingly, mothers in newly cemented houses reported less depression and greater life satisfaction.) By 2005, Piso Firme had spread to other states, and 300,000 households — about 10 percent of dirt-floor houses in Mexico — had taken part in the program.

It helps if the street outside the house gets paved, too — not so much for health reasons as for economic ones. Economists Marco Gonzalez-Navarro and Climent Quintana-Domeque found in a 2010 study that paving the street in the town of Acayucan, Mexico, added more than 50 percent to land values and caused a 31 percent rise in rental values. It also considerably increased households’ access to credit. As a result, households on paved streets were 40 percent more likely to have cars.

While the concrete mixers are there, why stop at the edge of town? Paving roads in rural areas has enormous human benefits — and not just by putting millions of people to work worldwide. Research by economists Shahidur R. Khandker, Gayatri B. Koolwal, and Zaid Bakht found that paved roads increased agricultural wages by 27 percent and output by more than 30 percent. It also increased school enrollment by as much as 14 percent.

Even fixing potholes helps — a lesson that applies as much in Washington and New York as it does in La Paz and Lagos. World Bank estimates for Latin America suggest that if infrastructure were properly maintained, the region’s GDP would be boosted by as much as 40 percent.

Of course, there are considerable environmental factors to account for: Making and pouring concrete and asphalt is a big source of greenhouse gases, and roads generate traffic, which means more exhaust and carbon emissions. Not to mention that building new roads in a pristine forest is a pretty surefire way to lose that forest to loggers, often without much in the way of economic returns. Concrete certainly is not a recipe for smart development of the Amazon — and countries would do well to balance new roads with higher carbon taxes.

But a little concrete can go a long way toward cementing a better life for millions.