China's population to decline

For the first time since Mao's Cultural Revolution 50 years ago, China's 1.4b people may decline, according to some calculations. China denies it. [FT]

The 'One Child Policy' was in effect for 35 years until it was ended in 2015. Some think the government will now incentivize or pressure citizens to have more children.

India is a close second for the largest population, with 1.38b, but their population is expected to continue increasing.