More than 3 million Indian officials are to spend a year counting every single person in the world’s most populous nation, a mammoth task delayed in part by the COVID-19 pandemic.

The once-in-a-decade population survey, originally due in 2021, will start on April 1 with a short window for citizens who wish to register themselves online, the government said on Monday.

There will then be two phases of ⁠physical door-to-door surveys. The first will list houses and housing conditions, the second - inhabitants and their economic and social parameters, Census Commissioner Mritunjay Kumar Narayan told reporters.

With a population of more than 1.4 billion people, India overtook China in 2023, according to the United Nations Population Fund.

Analysts and economists do not see the size of India’s population as a cause for alarm. The government has long hailed its predominantly young population as an opportunity to create a large pool of skilled workers while many major ⁠economies struggle with declining and ageing workforces.

The census will also collect details of castes, Narayan said. The rigid social stratification system dates back thousands of years and pervades Indian life and politics.

There are scores of caste-based political parties, and many state institutions must offer affirmative action ⁠quotas to the so-called lower castes for employment and college places.

Supporters have stressed the need for data on those deserving government assistance, while critics say caste has no place in a ⁠country with ambitions of becoming a major world power.

India recorded its castes in 2011 for the first time in 80 years, but the data was not fully ⁠publicised amid concerns about its accuracy.

The census is expected to conclude next March. Narayan said several data sets from the census, being recorded digitally for the first time, would be released soon after.