UNITED NATIONS, July 13, (AP): The world’s population is expected to grow by more than 2 billion people in the next decades and peak in the 2080s at around 10.3 billion, a major shift from a decade ago, a new report by the United Nations said Thursday.

The report — released on World Population Day — says the global population is then expected to decline to around 10.2 billion by the end of the century.

John Wilmoth, head of the U.N. Population Division which prepared the report, said the probability that the world’s population will peak within the current century is quite high – about 80%.

“This is a major change compared to the United Nations projections from a decade earlier when the estimated probability the global population would reach a maximum, and thus the growth would come to an end during the 21st century, was around 30%,” he said.

Bucknell University mathematics professor Tom Cassidy told AP that newly published research in the journal Demography that he co-authored also calculates that population is likely to peak before the end of the century.

According to the World Population Prospects 2024 report, the earlier-than-anticipated population peak is due to several factors, including lower fertility levels in some of the world’s largest countries, especially China, whose population is projected to drop dramatically from 1.4 billion in 2024 to 633 million in 2100.

Globally, women are having an average of one fewer child than they did in 1990, the report said, and in more than half of all countries and territories, the average number of live births per woman is below 2.1. That’s the level needed for a country’s population to maintain its size without migration.

Nearly 20% of the world — including China, Italy, South Korea and Spain — have “ultra-low” fertility, with women having fewer than 1.4 live births, the report said. In China, the current number is just around one birth per woman, Wilmoth said.

U.N. Assistant Secretary-General for Economic Development Navid Hanif told a press conference launching the report that the expectation the world’s population in 2100 will be lower than anticipated “represents a major shift compared to a decade ago, with important policy implications for the sustainability of our planet.”

According to the report, in 2024 population has already peaked in 63 countries and territories, including China, Germany, Japan and Russia. In this group, the total population is projected to decline by 14% over the next 30 years.

In another 48 countries and territories — including Brazil, Iran, Turkey and Vietnam — the population is projected to peak between 2025 and 2054, the report said.

For the remaining 126 countries and territories, including the United States, India, Indonesia, Nigeria and Pakistan, the population is expected to increase through 2054, “and, potentially, to peak in the second half of the century or later.”

For nine of those countries — including Angola, Central African Republic, Congo, Nigeria and Somalia — the U.N. is projecting very rapid growth, with their populations doubling between 2024 and 2054.

While these differences are striking, Wilmoth said, “it’s important to understand that all populations are following a similar path.”’

“The differences stem from countries being at different stages of the demographic transition towards longer lives and smaller families,” he said.

Wilmoth cited additional key findings in the report: Following the COVID-19 pandemic global life expectancy is rising again. By 2080, people aged 65 and older will outnumber children under 18 years of age. In some countries, immigration will be “the main driver of future growth.” And gender equality and women’s empowerment can help counter population growth.

The world’s population has grown dramatically in the last 75 years, from an estimated 2.6 billion in 1950 to 8 billion in November 2022. Since then, it has increased by roughly 2.5% to 8.2 billion.

Kathleen Mogelgaard, president and CEO of the Washington-based Population Institute, said Thursday’s new estimates underscore “an increasing demographic divide around the world.”

While it identified more than 100 countries and territories whose populations have already peaked or will do so in the next 30 years, she said, it shows even more where population will keep growing, many of them among the world’s poorest nations.

The U.N.’s Hanif said rapid population growth is likely to magnify the scale of investments and efforts required to eradicate poverty and hunger, ensure universal health care and education in countries facing severe economic, social and environmental challenges.

Conversely, he said, countries where fertility is low that face rapid population declines may require innovative policies to deal with labor market, social protection, and national security ramifications.

Looking ahead, the report compares the world’s 10 most populous countries today with their projection of the 10 most populous countries in 2100.

India tops both lists followed by China, though with a much smaller population at the turn of the century. The United States is in third place today but is replaced by Pakistan in 2100 and drops to sixth place -- behind Nigeria in fourth and Congo in fifth.

Right behind the U.S. in 2100 are Ethiopia, Indonesia, Tanzania, and Bangladesh. Brazil, which is the seventh most populous country today drops to 12th place at the end of the century.

Wilmoth said nobody knows what the world will be like when the world population peaks in the 2080s and the population is likely to be just one part of it, “but not necessarily the largest or the determining part.”

“What really matters is our behaviors and the choices we make,” Wilmoth said.