The world’s population will rise to 11.2 billion by 2100 from the current 7.6 billion, latest projections put out by the UN population division suggest. A billion have been added since 2005, and another billion are likely to be added by 2030 according to this forecast.

India’s population, currently estimated at 1.34 billion, is projected to rise to 1.51 billion by 2030 and further to 1.66 billion by 2050 before declining to 1.52 billion by century end.

Although China is currently the world’s most populous country with 1.41 billion, in 2024 both countries will have about 1.44 billion each. After that, India’s population will continue to grow while the Chinese population will remain stable till the 2030s and then decline.

According to the projections, nine countries led by India, Nigeria, Democratic Republic of the Congo, Pakistan, Ethiopia, Tanzania, the United States, Uganda and Indonesia will account for more than half the growth in global population between now and 2050.

In the process, Nigeria will overtake the US as the third-most-populous country in 2047. That’s remarkable considering Nigeria’s current population is estimated at 191 million to 324 million of the US. Thirty years on, the numbers are projected at 387 million and 385 million respectively.

Predicting population growth is a difficult art and the UN’s mandarins constantly have to juggle factors like fertility rates (how many children being born to women) in different regions, mortality or death rates, and the newly added “population momentum”, which happens because a more youthful population will promote faster population growth. This momentum factor has been added for the first time this year after previous years’ projections by the same agency were seen to come up short.

While fertility rates are dipping globally, some regions like Africa see a much lower decline from 5.1 to 4.7 while in Asia it has fallen from 2.4 to 2.2. Europe has seen an increase in fertility from 1.4 births per woman in 2000-2005 to 1.6 in 2010-2015.

However this is still below the “replacement level” of fertility that is taken as 2.1 births per woman. The replacement rate is the birth rate at which a population exactly replaces itself in one generation without any migration.

The crucial importance of fertility rates in estimating future populations is illustrated in the latest report. If fertility rate was just half a child more than what is assumed for every country, global population will reach 10.8 billion in 2050 instead of the projected 9.77 billion and 16.5 billion in 2100 instead of 11.18 billion.

Conversely, just half a child less than assumed now would mean world population would be just 7.3 billion in 2100.

Dropping fertility rates have led to the phenomenon of aging societies. Europe has an elderly population of 25% expected to reach 36% by 2100.

Compared to 2017, the number of persons aged 60 or above is expected to more than double by 2050 and more than triple by 2100, rising from 962 million in 2017 to 2.1 billion in 2050 and 3.1 billion in 2100. The reason behind a rising elderly population is rise in life expectancy, which jumped by four years in just a decade. The report also points out that 51 countries are expected to show declining populations between 2017 and 2050.

83 countries show below replacement level fertility rates but many are showing fluctuations with occasional rises and dips. China, US, Russia Germany, Iran, UK are some of such countries.

