The latest United Nations figures claim the world’s population is 8.2 billion, projected to peak at 10.3 billion by the mid-2080s. This has always been a rough estimate because you can never count all the people in the world one by one. Some countries have sophisticated censusing systems that fairly accurately track their populations, while others lag behind greatly. For instance, an estimated 850 million people in the world don’t have any identification documents.

So how many people are there truly in the world? There’s no way to tell for sure, but a controversial new study suggests that we may be underestimating the number of people living in rural areas by as much as 84%.

Could the World’s Population Be Much Higher Than We Thought?

The researchers from Aalto University in Finland who reported these findings never meant to challenge global population estimates. Initially, they simply wanted to know how many people were displaced by dam construction. They examined 307 dam projects across 35 countries, including China, Brazil, Australia, and Poland. These projects, completed between 1980 and 2010, required the resettlement of thousands of people.

But when they tried to quantify exactly how many people were displaced by the dams, they went down a rabbit hole that ultimately led them to a major discrepancy. Based on the reported displaced people, the researchers estimated the population of these rural areas before the dams were built. When they compared these figures to five major population datasets — which divide regions into grids and estimate the number of people in each square — they found that, on average, the datasets undercounted rural populations by 53 percent. In some cases, the estimates were off by as much as 84 percent.  In other words, even the best datasets are only capturing about half of the people living in rural areas.

“We were very surprised to see how large this underrepresentation is,” Josias Láng-Ritter, a researcher at Aalto University in Finland, told New Scientist.

Impacts of Undercounting

Population datasets are often calibrated for urban environments, where population density is high and data is more accessible. But rural areas are harder to map, and the data we have is often incomplete. In remote regions, census takers may struggle to reach every household, and communities affected by conflict or poverty may be overlooked entirely.

Many of these modern population datasets also use satellite data to finesse their estimates. Urban areas, with their dense infrastructure and bright nighttime lights, are relatively easy to map. But rural villages, often hidden by trees or made up of small, scattered buildings, can be nearly invisible from space.

Undercounting can have major implications. Governments and organizations rely on these datasets to plan infrastructure, allocate resources, and respond to disasters. If the data is wrong, the consequences can be dire. For instance, a disaster risk map that underestimates rural populations might lead to insufficient emergency services in those areas. Similarly, healthcare planning based on flawed data could leave rural communities without adequate access to medical care.

With nearly half of the world’s population still living in rural areas, accurate data is paramount for achieving the United Nations’ Sustainable Development Goals, which aim to ensure that no one is left behind.

It Needs Further Discussion

So, does all of this mean that there are billions more than officially reported in the UN data? The researchers in Finland didn’t want to recklessly offer a global population estimate. They recognize the limitations of projecting global figures from potential undercounting in rural areas surrounding dam projects.

Much of the study’s data comes from China and other parts of Asia, which have always been prone to undercounting, and may not apply to countries with more robust registration systems, such as Finland or Australia. If we’re really undercounting populations by such a massive amount, it’s reasonable to assume that governments should notice. Such a discrepancy should be reflected in other metrics, such as energy use, food production, and even mobile phone usage.

However, Láng-Ritter still believes his team is onto something.

“The countries we looked at are so different, and the rural areas we investigated have very different properties,” he says. “We’re quite confident that it gives a representative sample for the whole globe.”

Whatever may be the true size of the world’s population, these findings might spark a broader conversation about the limitations of our population datasets and the need for more accurate mapping tools. The Finnish researchers also plan to expand their analysis to include more recent data, as the current study only covers up to 2010.

The findings appeared in the journal Nature Communications.