A new study finds that the world population is likely to peak at 9.7 billion in 2064, and then decline to about 8.8 billion by 2100. The major reason behind this is a fall in fertility rates.

By 2100, 183 of 195 countries will not have fertility rates required to maintain the current population, with a projected 2.1 births per woman, researchers from the Institute for Health Metrics and Evaluation at the University of Washington’s School of Medicine said.

According to researchers, around 23 countries including Japan, Italy & Spain, will see their population decline by over 50%.

A study published by The Lancent, forecasts a decrease in the working-age population in countries such as China & India which will cause problems in their economic growth, labour forces and social support systems.

It is also estimated that by 2100, there will be 2.37 billion people over 65 years. And the population of people under 20 will be 1.7 billion. This means that people over the age of 80 will increase by 6 times while children under the age of 5 to decrease by 40%.