Is the UN correct in saying that the world has 8 billion people?

The UN estimates that the world will reach the 8 billion people mark this Tuesday (15th). Symbolism aside, experts consider that it is quite unlikely that the number will be reached exactly on this day, this month and perhaps this year, although the real figure does not vary much, either up or down.

In 2012, for example, the United Nations estimated that the world would reach the 8 billion people mark in 2024 alone. Five years later, the projection was brought forward to 2023 and, this year, it was recalculated to November.

The same deviation happened when the UN projected the 7 billion mark. The official announcement was in 2011, but reviews by the organization itself stated that this number had been reached a year earlier. Such variation is justified by the constant changes in the global mortality and fertility rates.

According to Enrique Pelaez, professor of demography at the National University of Cordoba, the UN tends to be wrong in the second index, which measures the number of children per woman. The current world fertility rate is 2.3 and is expected to remain above 2 until 2068.

For Pelaez, however, the real index should fall faster than announced. He gives examples from the 1990s, when the UN estimated a much slower drop in the number of children per woman than actually occurred. The lag affected projections of the global population in the following years: in 1992, the entity pointed out that 2025 would start with 8.5 billion people; today predicts 400 million fewer people.

Another factor that contributes to the margin of error in projections is the quality of data from underdeveloped countries in Africa, Asia and Latin America. Bolivia, Paraguay and the Dominican Republic, for example, do not have advanced systems to filter vital statistics, which interferes with fertility and mortality rates and the number of marriages and divorces in these countries and, consequently, in the world.

Furthermore, the UN estimates that more than half of the projected increase in global population by 2050 will be concentrated in just eight countries: Democratic Republic of Congo, Egypt, Ethiopia, India, Nigeria, Pakistan, Philippines and Tanzania – countries either emerging or underdeveloped with generally disqualified data collections. The margin of error in Nigeria, for example, is so great that the United Nations projects that the African country could have, in 2100, at the limit, between 300 million and 1.3 billion people.

Also weighing on the lag is the delay in renewing censuses, intensified by the pandemic – as happened in Brazil. All UN projections, by the way, come from national surveys and censuses.

The fact is that variations in global indices have little or no influence on the formulation of future public policies. This is because government actions are taken at the local level and, thus, the lag in Bolivia’s accounts, for example, does not affect the public policies of other countries at all.

“There is no public policy for the whole world, except for the Paris Agreement and other environmental treaties. In practice, it matters little whether the global population is 100 million more or 100 million less”, says José Eustáquio Alves, PhD. in demography and former professor at the National School of Statistical Sciences.

Furthermore, global projections are not influenced by the impacts of migration, one of the most flexible and difficult movements for demographers to project. In Venezuela, highlights Pelaez, the UN considers that people who sought refuge in neighboring countries in recent years will return at some point – the forecast considers the pattern detected in similar situations in other nations. “But what if they don’t come back?”

In this case, the sum of 8 billion would not change anything, since the Venezuelan refugee would continue to be counted by the country in which he is and, consequently, by the global population projection.

But these variations can, indeed, generate derangements in local public policies. Simple examples are vaccination rates above 100% in some municipalities during the Covid-19 pandemic – which can be explained by the lag between population projections and the actual number of residents.

Errors and lags aside, the fact is that the UN projections are fundamental in the formulation and monitoring of public policies. They are used, for example, in the calculation of almost a quarter of the indicators that monitor the achievement of the Sustainable Development Goals – tools to meet targets for reducing social inequality.

“To make any policy, it is necessary to know the size of the population that will receive it. Without these projections, it is impossible to monitor public policies”, says Pelaez.