Night Light Development Index correlates strongly with the U.N. Human Development Indicator, other welfare metrics
Gross Domestic Product and its cousin, GDP per capita, have long been the most widely accepted measures of national and human wellbeing around the globe. But for nearly as long, GDP and per-capita GDP have been seen as deeply flawed.
After all, GDPâa number representing the total amount of goods and services produced by a nation within a specified period of timeâdoesnât distinguish spending on, say, education and cigarettes. Likewise GDP doesnât measure anything without a market price attached and completely disregards the âinformal economyâ volunteering, household work, childcare, subsistence agriculture and more.
"AVĂûÊȘers are able develop ratios of data from nighttime satellite imagery to GDP and see where there are discrepancies.ÌęThe satellite imagery tracks closely with broader measures of human wellbeing such as the so-called âhappiness index and the U.N.âs Human Development Indicator.â
Another limitation: GDP measures total economic activity, but not the distribution of that activity, also referred to as âinequality.â That important distinction is currently at the center of political debate in the United States, as incomes disparity has widened significantly in recent decades.
Also, governments too often manipulate GDP, and methods of determining GDP vary widely around the globe.
âThere is no standardized method of for gathering data (on GDP) throughout the world,â says Tilottama Ghosh, a research Ìęassociate at CU-Boulderâs Cooperative Institute for AVĂûÊȘ in the Environmental Sciences and co-author of âUsing Nighttime Satellite Imagery as a Proxy Measure of Human Well-Being,â published in the November issue of Sustainability.
But Ghosh has been working with other researchers from the National Oceanic and Atmospheric Administration, the University of Denver and elsewhere to demonstrate that nighttime satellite imagery can serve as an effective proxy measure of human well-being.Evaluating imagery from the U.S. Defense Meteorological Satellite Program, which goes back to 1992, and other sources, the research team starts with the general proposition that more lights on a satellite imageâmeasured in pixels per square kilometerâcorrelate with higher levels of development.
Think of the famous photos from space showing North Korea to be almost a black hole while South Korea is ablaze with light. Or the comparison between a brightly lit Tokyo and the heart of Africa.
But the work is more refined than that. For example, the researchers are able develop ratios of data from nighttime satellite imagery to GDP and see where there are discrepancies.
The satellite imagery tracks closely with broader measures of human wellbeing such as the so-called âhappiness indexâ and the U.N.âs Human Development Indicator.
âOur Night Light Development Index correlates strongly with the long-established metric of the HDI used by the United Nations that is based on multi-dimensional composite of things like GDP/capita, life expectancy, and average years of education per capita,â says Paul C. Sutton of the Department of Geography and the Environment at Denver University, one of Ghoshâs co-authors.
Whatâs more, satellite provides data more immediately than on-the-ground surveys of well-being, which can take years.
âThese proxy measures are updated much more frequently,â Ghosh says.
Development is not without its consequences, however. Satellite imagery also shows what ÌęSutton calls an âecological deficit.â In other words, zero pixels per square kilometer shine forth from the deepest Amazon, while crowded cities, with their attendant issues of pollution and resource depletion, blaze with light.
âThe more developed countries of the world are taking more from the environment,â she says.
To date, a square kilometer has been about the highest resolution available to measure light output. But satellites of the National Polar Orbiting Partnership between NASA and NOAA have since 2011 provided higher resolution imagery.
âOne of our main objectives is higher-resolution data, to be able to refine the measurements further. Once these data become available ⊠weâll have much superior quality for estimating socio-economic variables,â Ghosh says.