It turns out that while density equals efficiency, “megacity” does not necessarily equal density. Many megacity dwellers live outside those hyper-efficient city centers, Kennedy explains. Look at New York—if you live in Manhattan or parts of Brooklyn and Queens, you’re probably getting around on the subway. But if you live in Westchester, New Haven, or Newark? You’re probably driving your car—maybe not into the city center, but around it. And there are a lot of you. That’s why New York is almost off the chart in its consumption of transportation fuel, despite all its great rail.
But not all megacities consume as many resources as New York. Look at the ones clustered at the bottom end of transportation energy use: Mumbai. Karachi. Lagos. Cairo. Delhi. These are also some of the cities that use the least amount of electricity per capita. Unfortunately that’s not because their electrical grids are super-efficient. It’s because not everyone living there has electricity. “There’s huge disparities between the amount of resources being used between the wealthiest megacities and the poorest ones,” Kennedy says. In the latter, the resource inputs aren’t enough to support a basic standard of living for all citizens…
So while developed-world megacities should consider reining in their gasoline and electricity use—or expanding center-city style efficient infrastructure to the ’burbs—growth (combined with smart policy) may be the answer to developing-world megacities’ woes. Which is good, because if one thing’s for sure it’s that megacities are growing, and they’re not going to stop.
So the issue may not really be density but a higher order issue of social class. In other words, efficiency is the result of different processes depending on the wealth and development of particular cities and countries. In wealthier countries, individuals have the resources to spread out and can afford to consume too much. On the other hand, poor countries have big cities with lots of residents who can’t afford to consume what they need.