Last year the United Nations set a goal of eliminating extreme poverty worldwide by 2030. That's an audacious target. One of the first steps—figuring out where the most impoverished people live—has proved surprisingly difficult. Conducting economic surveys in poor or conflict-prone countries can be expensive and dangerous. Researchers have tried to work around this limitation by searching nighttime satellite images for unusually dark areas. “Places lit up at night are generally better off,” explains Marshall Burke, an assistant professor of earth science systems at Stanford University. But this method is imperfect, especially for differentiating between grades of poverty. From space, at night, mild and extreme poverty look the same—dark.