Determine GDP growth rate from outer space

According to a new study conducted by three economists from Brown University, space satellites can bring new perspectives on measuring economic growth. In a research report serving the National Bureau of Economic Research, J. Vernon Henderson, Adam Storeygard and David N. Weil introduced a new model that estimates the value of a country's gross domestic product (GDP). or territories by using night light satellite images of the area.

In many parts of the world, reliable data on economic growth are difficult to obtain - especially sub-Saharan and other developing countries. The authors cite the evidence from Penn World Tables, one of the standard documents on the nation's income data, which ranks countries from A to D according to the quality of GDP data and prices. While most industrialized countries are ranked A, almost all sub-Saharan African countries only stop at C or D, with deviations of up to 30% -40%. Some countries do not even appear in this rating, including: Iraq, Myanmar, Somalia, and Liberia.

To improve these estimates, Henderson, Storeygard and Weil introduced a method of incorporating published income data with changes in 'night light' in a city when viewed through defense images. Fine shooting from outer space. With the use of photographs taken from the US Air Force's weather satellite, they looked at changes in light density for 10 years. 'Consuming almost all goods at night requires light,' they write. 'As income increases, per capita use of light also increases, in both consumer activities and investment activities. '

Increasing the amount of light in the night is synonymous with economic growth in Poland and Eastern Europe between 1992 (top, left) and 2002. Poland is located in the upper left quadrant in each picture. (Photo: NOAA and the US Weather Forecasting Agency)

When researchers applied new methods to income of countries with low data quality, the results were quite different. For example, for the Democratic Republic of Congo, the calculation of light intensity shows that the annual GDP growth is 2.4%, while the official figure is -2.6% for the same time period above. The Congo seems to be growing faster than announced. In contrast, Myanmar is expected to grow 8.6% per year according to published data, but data on night light only gives annual GDP growth of 3.4%.

Henderson, Storeygard, and Weil said they did not consider light intensity data as a substitute for specialized agency numbers, but when presented with existing data of organizations like Ngan World rows, light density can provide a more complete indicator of the economic situation of nations.

'We hope that people will start using these numbers when they have no data on economic growth . or when the numbers are not very reliable,' Henderson, economic lecturer learn, speak. 'This is just a way to contribute to more accurate estimates.'

The second part of the paper presents the first causal relationship between local agricultural productivity and the increase in income in cities. By examining 541 cities in 18 African countries over nine years, the authors concluded that increased agricultural production actually had a significant impact on economic activity in the cities of that country.

Storeygard added that this research is really a work of collaboration. Weil studies extensively on many different aspects of economic development, while Henderson is often interested in measuring regional or local growth in a country. Soreygard has extensive experience in using satellite and geographic data.'This is a work that uses knowledge in all three areas that we study,' Storeygard said. 'I don't think one of the three can do this work alone.'