Experts are warning that millions of people around the world aren’t being counted in census data, leaving policy makers in the dark about the populations they govern. They say a “quiet crisis” is unfolding with census data not being published due to concerns about declining response rates and the accuracy of data.
In a paper published in Science, researchers from the University of Southampton and the Columbia Climate School point to a “perfect storm” of disruptions from the COVID-19 pandemic, declining confidence in institutions, and collapsing international support.
“We live in an era of seemingly unlimited data, yet some of our most essential demographic information is deteriorating, introducing known and unknown bias into decision making,” says co-author Dana Thomson, Associate Director of Science Applications at the Center for Integrated Earth System Information (CIESIN), which is part of the Climate School.
Thomson and her coauthors say recent cuts to international aid budgets from the U.S., the U.K. and other European countries will worsen the situation.
Decisions about where to build a hospital or how to allocate resources for schools rely on knowing how many people live in different places and who they are. This information is especially important during a crisis, such as an outbreak of disease or a natural disaster.
“Lack of census data compromises all areas of public administration, but we don’t see these statistics in the same way as other vital infrastructure, like bridges or roads,” says lead author Jessica Espey, from the University of Southampton and deputy director of its WorldPop research program. “When groups are not counted, they can be left off the policy agenda. That political underrepresentation and the inadequate resource allocation that follows can have pernicious effects.”
Governments have used census data for thousands of years to direct resources and anticipate future challenges and opportunities, such as an aging population or a burgeoning younger one.
But the percentage of the world’s people covered by up-to-date censuses has declined. Of the 204 countries that carried out a census between 2015 and 2024, 24 of them haven’t published their results. They represent a quarter of the world’s population.
Post-enumeration surveys, which independently assess the completeness of a census, also suggest a decline in accuracy and coverage. For example, the 2020 U.S. census likely undercounted the Latino population by 2.9 million people, while South Africa’s 2022 census undercounted the country’s overall population by up to 31%.
The COVID-19 pandemic disrupted traditional house-to-house interviews and impacted funding. The researchers also highlight growing distrust in national governments, such as the fear some communities have that immigration-related law-enforcement or AI-supported decision making will use their data against them. Others worry about the threat of data leaks and cyber-attacks.
In February of this year, the Trump administration cut support for the Demographic and Health Surveys (DHS) program, which provided vital health data across 90 countries for four decades. Other countries like the U.K., France and the Netherlands have reallocated development assistance to defense spending, reducing both direct bilateral assistance and U.N. multilateral contributions.
The researchers say new technologies, such as AI-derived building footprints from satellite images, can support the planning and implementation of census rounds and potentially reduce costs, pointing to recent success in the Democratic Republic of the Congo.
They also say governments need to do more to build trust, demonstrate how census data affects people’s daily lives and be transparent about how this data is used to inform decisions.
“In an era of growing challenges, from climate change to economic inequality, accurate population data is not a luxury–it is essential infrastructure for healthy, resilient, functioning societies,” says WorldPop Director Andrew Tatem, one of the paper’s coauthors.
“The current undercounting of populations creates a negative feedback loop, leaving governments with less accurate information on the communities most in need. This threatens both statistical accuracy and the very foundations of equitable governance.
By combining technological innovation with renewed public trust and international cooperation, we can ensure that everyone is counted–and everyone counts.”
Adapted from a press release written by Steve Williams, University of Southampton.
Press Contact: Francesco Fiondella, Columbia Climate School, [email protected] or 1-646-321-2271.