Night light data reveals limited urban growth in Bihar

A comparison of night light data from 2013 and 2023 shows that most Assembly constituencies in Bihar continue to remain predominantly rural. Only a few constituencies have shown significant growth in nighttime luminosity, primarily in Patna, which was already among the more urbanised parts of the State.

Nighttime illumination can serve as a useful proxy for gauging human activity and electricity usage in an area. A higher concentration of night lights often reflects not just street or vehicular lighting, but also ongoing economic activities such as construction or roadwork. Together, these patterns of brightness offer a visual measure of urban growth and development.

The Hindu Data Team uses this method to classify constituencies in a State as rural, semi-rural, semi-urban, or urban. This approach is adopted due to the absence of up-to-date official data on the subject, and as administrative boundaries vary from political boundaries.

Slow transitions

The chart shows the share of Bihar’s Assembly constituencies across different levels of nighttime illumination — very low and low (mostly rural and some semi-rural areas), medium (semi-rural and semi-urban areas), and high and very high (largely semi-urban areas and cities) — in 2013 and 2023.

In 2013, nearly 90% of Bihar’s Assembly constituencies fell under the “very low” illumination category. By 2023, that figure had dropped sharply to just 16%, with a significant portion of these seats shifting into the “low” and “medium” illumination bands, suggesting that some rural areas have gradually transitioned into semi-rural ones.

In contrast, movement to the “high” and “very high” illumination categories has been negligible. The share of constituencies in the “very high” band — representing mostly cities — rose only slightly, from 0% to 1.6%, while the proportion in the “high” band has remained unchanged. In 2023, all constituencies in the “very high” illumination band were located in Patna, while only three constituencies outside the capital — Gaya Town, Bhagalpur, and Muzaffarpur — fell into the “high” luminosity category.