Rural population estimates underestimate the number of actual people living in these areas by at least half, researchers argue. However, the findings are contested by demographics. Demography says such underestimation is unlikely to change the head count of a nation or world.

Josiasláng-ritter And while his colleagues at Aalto University in Finland were working to understand the extent to which the dam construction project resettled people, they continued to get numbers that differed significantly from official statistics while estimating the population.

For the purposes of the investigation, they used data on 307 dam projects in 35 countries, including China, Brazil, Australia and Poland, completed between 1980 and 2010, and obtained the number of people reported to have resettled in each case as the population of the area prior to evacuation. We then cross-checked these numbers to break down the area into a square grid, and estimated the number of people living in each square to reach the total.

Láng-Ritter and his colleagues discovered that what they say is a clear contradiction. Their analysis shows that the most accurate estimates increased the actual number by 53% on average, while the worst was 84%. “We were very surprised to see how big this underestimation is,” he says.

The official UN estimate of the world population is around 8.2 billion, but Láng-Ritter says the analysis shows perhaps much higher, but refuses to give a specific number. “Today, population estimates are likely to be conservative accounting, and there is reason to believe that these over 8 billion people are significantly more common,” he says.

The team suggests that these counting errors will occur. This is because rural census data are often incomplete or unreliable, and population estimation methods have historically been designed for the best accuracy in urban areas. Correcting these systematic biases is important to avoid inequality for rural communities, researchers suggest. This can be done by improving census in such areas and recalibrating the population model.

If rural population estimates are far more abolished, it could have a significant impact on the provision of government services and plans, Láng-Ritter said. “The impact may be very large because these datasets are used for so many different types of actions,” he explains. This includes planning transportation infrastructure, building health facilities, and risk reduction efforts in natural disasters and epidemics.

However, not everyone is convinced by the new estimate. “The study suggests that the number of local populations in places where you live in the country is incorrectly estimated, but it is not clear that this necessarily implies that the national estimates of the country are incorrect.” Martin Cork At Stockholm University, Sweden.

Andrew Tame The University of Southampton in the UK will oversee WorldPop. This was one of the data sets that the study suggested, lowering the population by 53%. He says that grid-level population estimates are based on combining high-level census estimates with satellite data and modeling, and that the quality of satellite images before 2010 is known to inaccurate such estimates. “The more time we go back, the more those problems come,” he says. “I think that’s something that’s well understood.”

Láng-Ritter believes new ways are needed as data quality remains a problem. “With the data has improved dramatically within 2010-2020, it is very unlikely that the issues we identified have been fully resolved,” he says.

Stuart Giel Basten In Hong Kong, the University of Science and Technology points out that most of the team’s data comes from China and other parts of Asia and may not apply globally. “I think it’s a very big jump to say that there is a very large undercount in other places like Finland, Australia, Sweden, etc. with a very sophisticated registration system based on one or two data points.” láng-ritter admits this limitation but supports the work. “The countries we saw are very different and the rural areas we surveyed have very different characteristics, so we are confident we will provide a representative sample of the whole of the globe.”

Despite some reservations, Gietel-Basten agrees to Láng-Ritter on one point. “I certainly agree with the conclusion that we should not only invest more in rural data collection, but come up with more innovative ways to count people,” he says.

But the idea that the official world population should expand to billions of people as “unrealistic,” Gietel-Basten says. Tatem is more convincing. “If we’re really insufficient in that mass, it’s a massive news story and it goes against everything in the thousands of other datasets,” he says.