Two more decades of growth for China, four more for India: within 40 years the world’s two population giants will together inhabit close to 3 billion people.

Indeed, our population growth comparison series continues. It is our attempt to help you better digest the wealth of information in the World Population Prospects 2010 Revision. Today we take a closer look at China and India, the two at the top.

30 years birth restrictions equals 30% population growth

There is a big misconception about the Chinese one child policy, namely that the title represents the content and that the Chinese population would only be allowed a single child per couple. There are many exceptions, which is why in the 30 years since implementation of that demographic policy, the total Chinese population grew by some 300 million people, to 1,341 million in 2010.

India has also surpassed the one billion milestone. Last year the country had an estimated population of 1,225 million people.

And that’s where both the comparison and respective populations grow apart. Last year the Chinese population grew by 0.5 percent. India’s population grew 1.4 percent. On a timescale of decades this can make a huge difference – as the below table, which comes straight from the UN’s report of May 2011, illustrates.

World’s 20 largest populations in 2050

The table shows the forecast top 20 of most populous countries by 2050, right before Nigeria surpasses the US [even though the US is the only big western country with considerable population growth – an extra 93 million people between 2010 and 2050], Russia down to place 14, and all EU member states long gone – although we see one aspiring country just entering the list.

Right at the top the 2050 picture is in a sense still familiar, with two true giants. But they did switch places, and with a considerable margin too. According to the UN’s calculations in 2050 India will have 1,692 million inhabitants, almost 400 million more than China, which will have a gradually declining population from 2030 onwards, whereas in 2050 India would still be on the growth track. These demographic differences will of course manifest themselves not just in population size, but also in the economically very relevant age distribution.

Population age development over 21st century

But, as the below graph shows: population aging is a self-solving problem. China would just have to wait till 2100 to get to exactly the same median population age of India – at a nice and productive 46 years.

© Rolf Schuttenhelm | www.bitsofscience.org