Currently, population of China is about 70 million persons higher than population of India according to United Nations Estimates: 1.38 against 1.31 billions. Other sources' estimates of current population range from 1.37 to 1.40 billions for China and from 1.28 to 1.31 billions for India.
According to the United Nations' forecast, existing difference between populations of two countries will level off by 2022. Food and Agriculture Organization gives later date - 2024. OECD and UNCTAD predict that this will happen even lately - in 2028. On the contrary, World Bank's estimates propose that India will outpace China as early as in 2021 - in some 5 years. To compare projections from different sources in detail, visit our World in 2020 page.
Expectation that Indian population is to surpass that of China stems from the following assumptions. First of all, these two countries belong to different fertility groups. China is considered to be "low fertility" country while India generally refers to "intermediate fertility" countries. India, as well as China has already experienced substantial fertility decline as a result of implementation of National Family Planning Program in 1952, but in India it failed to achieve ultimate goal and did not lead to dramatic changes as contrasted with China. Moreover, share of urban population in India is significantly lower and is growing at a lower pace in comparison to China. The other factors behind rapid population growth in India are high illiteracy and poverty rates, immigration from Bangladesh and Nepal and decline in mortality rates.
All these features have resulted in the fact that India have already outpaced China in the contribution to the world's population growth. Thus, in the period 2010-2015 Indian population increased by 16 million persons - the highest value accounting for 19% of global population increase - while Chinese population grew by 7 millions - only half as much as Indian. India is expected to retain its leading position by this indicator in the long term 2015-2050 followed by Nigeria.
What for current annual population growth rate in countries under examination, it is estimated by different agencies from 1.2 to 1.32% in India and from 0.46 to 0.56% in China. And although population growth in India is constantly cooling down so that it is expected to drop below 1% by 2024 and below 0% threshold by 2069 it is not expected to become lower than that of China in the nearest 100 years. So, India is going to become world population leader for the long time.