U.N.: 9 Billion Humans By 2300

The world will have around 9 billion people in 300 years, according to a U.N. forecast. The current population is 6.3 billion.

But the U.N. Population Division said even a small shift in fertility levels could have an enormous impact on the planet's population.

The 9 billion estimate is based on the two-child family, but as little as an average of one-quarter of a child more or less per family would result in world populations in 2300 ranging from 2.3 billion to 36.4 billion, it said.

Previous long-range projections put the world population at 10-12 billion in 2200, said Joseph Chamie, director of the Population Division.

The new projections are lower, largely due to the continuing decline from high fertility rates in the developing world.

"This is certainly encouraging news since men and women are attaining control over the number and spacing of their children," Chamie said.

The projections for 2300 are "groundbreaking" because they are the furthest the United Nation has projected population; in the past it was only 150 years, Chamie said.

Developed countries will see substantial declines in population

Russia, Italy and Spain if their current fertility rates remained constant until 2300, Chamie said.

The U.S. population, which was about 76 million in 1900, doubled by 1950 to 158 million and by 2010 it will have doubled again to about 315 million, Chamie said. Today, it is 295 million.

In 2050, the United States will have 409 million people; in 2200, 470 million, and in 2300, 493 million, he said. But if current fertility rates remain unchanged, the population would hit 523 million by 2300.

The report, "World Population in 2300," also foresees far older people.

The median age of the world today is 26 years. By 2300, it will nearly double to 50 years, Chamie said.

Similarly, the world population 60 years and over will jump from 10 percent today to 38 percent by 2300 — and the percent over 80 will rise from just 1 percent today to 17 percent over the next 300 years, he said.

The expected population growth will also result in a redistribution of the world's population, Chamie said.

Africa's share will double from 13 percent today to 24 percent in 2300 while Europe's share will be halved from 12 percent to 7 percent, he said.

Asia will go from 61 percent today to 55 percent in 2100 and remain at 55 percent in 2200 and 2300, Chamie said. Latin America and the Caribbean, which account for 9 percent of global population today, will decline to 8 percent in 2100, and remain at 8 percent in 2200 and 2300.