Using data generated by the night lights, economists Praveen Chakravarty and Vivek Dehejia studied 387 of 640 districts in 12 Indian states. 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. And using this unique methodology, the economists documented income divergence in India.
Around 380 districts in 12 states were on average only a fifth as bright, compared to cities like Mumbai and Bangalore. Also, 90% of all the districts were only a third as bright at night when compared to the top 10% of all districts. And the ratio has apparently worsened between 1992 – a year after India embraced economic reforms – and 2013.
While the pre-1991 years show a modest trend towards convergence of income between different states, the years after show widening divergence. By 2014, the economists found, the average person in the three richest states (Kerala, Tamil Nadu, Maharashtra) was three times as rich as the average person in the three poorest states (Bihar, Uttar Pradesh and Madhya Pradesh).
Night lights pose their own challenges with data reading though . Issues like phases of the moon, aerosols, water vapour and ozone do affect readings. But the latest sensors on satellites have been throwing up richer spatial details like detecting lit roads and dimly lit sources. ( Story courtesy wires)