China and India have the world’s largest populations, respectively. Together, they make up 37% of the world’s total population. China has held the title as the world’s largest country for all of recorded population history, but that is soon to change. India is projected to overtake China as the world’s largest country in 2022. China’s population is projected to peak in 2028 and then start declining, and to drop below today’s level in 2045.
Chinese fertility began to decline sharply years before the one-child policy was put in place. In 1965-1970, women in China were having an average of 6.3 children each. Ten years later, in 1975-1980, they were only having 3.01. After the one-child policy was enacted in 1980, fertility fell further, reaching an estimated 1.55 children per woman in 2010-2015.
The fertility rate in India is rapidly declining as well, but it has not dropped as low as has China’s. As a result, the population growth rate is higher in India and has set the country up to grow to a larger number than the level that will be reached in China.
Source for population and fertility data: World Population Prospects, 2015 Revision, UN Population Division