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Measuring South Asia’s economy from outer space

Martin Rama's picture
New technologies offer an opportunity to strengthen economic measurement. Evening luminosity observed from satellites has been shown to be a good proxy for economic activity.
New technologies offer an opportunity to strengthen economic measurement. Evening luminosity observed from satellites has been shown to be a good proxy for economic activity.
Economic growth is a key concern for economists, political leaders, and the broader population.

But how confident are we that the available data on economic activity paints an accurate picture of a country’s performance?

Measuring Gross Domestic Product (GDP), the most standard measure of economic activity, is especially challenging in developing countries, where the informal sector is large and institutional constraints can be severe.

In addition, many countries only provide GDP measures annually and at the national level. Not surprisingly, GDP growth estimates are often met with skepticism.
 
New technologies offer an opportunity to strengthen economic measurement. Evening luminosity observed from satellites has been shown to be a good proxy for economic activity.

As shown in Figure 1, there is a strong correlation between nightlight intensity and GDP levels in South Asia: the higher the nightlight intensity on the horizontal axis, the stronger the economic activity on the vertical axis.
Figure 1 Nightlight intensity increases with economic activity
Figure 1 Nightlight intensity increases with economic activity

However, measuring nightlight is challenging and comes with a few caveats. Clouds, moonlight, and radiance from the sun can affect measurement accuracy, which then requires filtering and standardizing.

On the other hand, nighlight data has a lot advantages like being available in high-frequency and with a very high spatial resolution. In the latest edition of South Asia Economic Focus, we use variations in nightlight intensity to analyze economic trends and illustrate how this data can help predict GDP over time and across space.

We show that in the case of South Asia, predicted GDP numbers using nightlight intensity closely track official National Account measures at the aggregate level, and – as shown in Figure 2 – provide a granular picture of GDP per capita at subnational levels.

Figure 2 Nightlight data can be used to predict GDP per capita at the district level
Figure 2 Nightlight data can be used to predict GDP per capita at the district level
As we document in the report, nightlight intensity also yields new insights on recent economic developments. The major shocks experienced by Nepal in 2015 had very different impacts across districts. In Afghanistan, local surges in conflict reduced local growth for up to one quarter. And in India, demonetization had a short-lived effect at the aggregate level, but a noticeable impact on rural, unbanked and informal districts.
 
While providing new economic insights, big data from outer space is no replacement for more traditional – and terrestrial - statistical measurement.

New technologies can help reach new frontiers, but they cannot replace information gathered from censuses, surveys and administrative records that statistical agencies collect, curate and disseminate.
 
Unfortunately, many of these statistical agencies face important challenges.  Surveys do not cover the informal sector well, respondents are not always truthful, and information is not captured with sufficient spatial granularity.

Resources and capacity are limited, and in some cases, technical independence, access to information, and the protection of privacy need to be improved.

Building trust that growth figures do not come “out of the blue” will require a clear strategy toward stronger statistical systems.
 
Nightlight Satellite Imagery Opens New Frontiers to Measure Economic Activities
Nightlight satellite imagery opens new frontiers to measure economic activities. Based on their latest edition of the South Asia Economic Focus, World Bank Chief Economist for South Asia, Martin Rama and Economist Robert Beyer discuss how variations in nightlight intensity can help analyze and predict economic trends in South Asia.

 

Comments

Submitted by Biswanath Debnath on

I think many of us, who are good observants, know this, even without new technologies. I can cite a personal experience. In 1999, I was once returning to Trivandrum from Kanyakumari in southern India in the evening, roughly a 3-hour road journey. I reached Trivandrum around 10:00 pm. Kanyakumari is the southern tip of India. During the journey I noticed that from the southern tip towards north, less and less light in the shops along the highway. This clearly indicated that the Tamil Nadu state (where Kanyakumari is) is more vibrant than the Kerala state (who capital is Trivandrum). But, overall, as well acknowledged, the economic growth in southern India is better than that of other parts of India.

Submitted by Srinivas on

Although in this case Kerala is actually more "developed" than Tamil Nadu (HDI wise), I agree with you on the principle. We can see this more clearly on train journeys, counting the number of villages that are brightly lit compared to the ones that aren't. It's good that these new tools are being used to analyse our complex economy.

Submitted by Mohammad Ashadullah on

To me, informal sector should be taken for consideration and street side business. Some country apply closer of business after 8p.m and so economy on the basis of intensity of light may not correct but may be taken for consideration to some %.

Submitted by Bashir Abbasi on

Superb presentation regarding GDP with new approach. It has been even more easy and reliable for the countries to assess economy from federal governments to states and even more district level. The presenter is highly appreciable for such a great presentation.

Submitted by Nasiruddin Ahmed on

I found the contention of this assessment quite obvious from air flights! It is always observed from above that as the carrier approaches any city the intensity of lights below increases indicating increasing economic activity and share of GDP gowth.

Submitted by Joseph on

Along the western sea coast many lights are not seen. The reason for this is , I think, the lush vegetation in the area with many tall trees . If you take Kerala state as a whole,there is vegetation every where , even in most populated cities. But Kerala is one of the most developed states in India, if not the best. I see a loophole in the theory if this aspect is not given adequate consideration.

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