Are night lights on earth captured by satellites from outer space a good way to measure inequality? Economists Praveen Chakravarty and Vivek Dehejia certainly believe so. They acquired images grabbed by satellites from the US Air Force Defence Meteorological Satellite Programme. These satellites circle the earth 14 times a day and record lights from the earth's surface at night with sensors. They superimposed a map depicting India's districts on their images, allowing them to develop a unique data set of luminosity values, by district and over time. (BBC News)