A study by researchers from the Institute for Health Metrics and Evaluation at the University of Washington’s School of Medicine has claimed that the world’s population is likely to peak at 9.7 billion in 2064, and then decline to about 8.8 billion by the end of the century.

The study projects that 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.
The report predicts that the population of Japan will shrink from around 128 million people in 2017 to 60 million in 2100, Thailand will  shrink from 71 to 35 million, Spain from 46 to 23 million, Italy from 61 to 31 million, Portugal from 11 to 5 million, and South Korea from 53 to 27 million.
34 countries including China are  predicted to see their population decline by up to 50%.
The population of sub-Saharan African countries like Nigeria is expected to triple.
The researchers believe that the population of sub-Saharan Africa will grow from an estimated 1.03 billion in 2017 to 3.07 billion in 2100.
The study also projects major changes in the global age structure as fertility falls and life expectancy increases, with an estimated 2.37 billion people over 65 years globally in 2100, compared with 1.7 billion under the age of 20.