India could surpass China as the world's most populous country in 2023, each with more than 1.4 billion people, according to a United Nations report that warns that high birth rates will hamper economic growth.

The world's population, estimated to reach 8 billion by 15 November this year, could rise to 8.5 billion in 2030 and 10.4 billion in 2100 as the death rate slows, according to the report released on World Population Day.

India's population was 1.21 billion in 2011, according to the domestic census, which is conducted every ten years. The government postponed the 2021 census because of the COVID-19 pandemic.

The UN estimates that the world's population grew at the slowest rate since 1950, falling below 1 percent in 2020.

In 2021, the average global birth rate was 2.3 births per woman per lifetime, down from about 5 births in 1950. Global fertility is projected to drop to 2.1 births per woman by 2050.

Global life expectancy has fallen to 71 years in 2021 from 72.8 years in 2019, mostly because of the pandemic.

The United Nations said more than half of the world's projected population growth by 2050 will be concentrated in eight countries - the Congo, Egypt, Ethiopia, India, Nigeria, Pakistan, the Philippines and the United Republic of Tanzania.

Sub-Saharan Africa is expected to account for more than half of the growth expected through 2050.

However, the populations of 61 countries are projected to decline by 1 percent or more between 2022 and 2050 because of declining fertility.