The world population will peak at 8.7 billion people in 2055 and then decline to 8 billion by 2100, according to new research by Deutsche Bank. Its projections contrast drastically with previous forecasts by the United Nations (UN), which sees world population continuing to rise until 2100.
"The world is approaching a major turning point in its demographic trajectory and we think that the shift is likely to be sooner and sharper than mainstream projections suggest," said Deutsche's global strategist, Sanjeev Sanyal.
(Read more: China rethinks one-child policy as it ages rapidly)
The latest numbers from the UN put the world population at 7.2 billion. While the UN forecasts the global population will reach 10.9 billion in 2100, Deutsche Bank believes it will be only 8 billion.
Sanyal said that while developed countries have long had low birth rates, developing countries like China, Russia, South Korea and Brazil now have the largest declines in fertility. He argued that poorer countries needed a higher total fertility rate (TFR) -- the average number of live births per woman over her lifetime -– to maintain a stable population, due to higher levels of infant mortality.
He estimated that women in less developed countries needed to have an average of 2.3 babies for a stable population in the long-term. In contrast, most it is often said that an average of 2.1 babies per woman is enough to sustain a country's population, and does not adjust this according to wealth.
(Read more: Zafran: Betting on the population boom)
Sanyal said that fertility rates were well below replacement level in many developed countries, with Germany and Japan having TFRs of 1.4. But levels were also low in countries like South Korea, where TFR had fallen from 5 in the 1950s to 1.3 today, and Brazil, where TFR had dropped from 6.2 in the 1950s to 1.8 today.
"Given the above trends, we feel that the world's overall fertility rate will fall to replacement rate by 2025. In other words, reproductively speaking, our species will no longer be expanding – a major turning point in history," he said.
In particular, he forecast a large decline in the Chinese workforce, irrespective of the removal of the one-child policy.
"Due to a skewed gender ratio, we found that China no longer has enough child-bearing age women to stabilize its population," he said.
(Read more: India's secret weapon: Its young population)
As China's population declines, Deutsche Bank said that countries like Indonesia, the Philippines and India will become key players in the global workforce, while the United States will continue to experience a growing work pool into the 2050s.