China on Sunday kicked off its once-a-decade national population census, with about 7 million staff to visit homes for registration work.

The country, which has the world’s largest population, for the first time will use mobile apps to help crunch the massive numbers.

Carrying out the census is critical to understand the population size, structure and distribution, Xinhua news agency quoted Ning Jizhe, deputy head of the National Development and Reform Commission, as saying.

It will provide important and basic information for the national strategy of responding to the challenge of population aging, as well as for the promotion of high-quality development, said Ning.

The census collects data including name, ID number, gender, marital status, education and profession of Chinese citizens.

Ning urged efforts to complete the census with high quality to provide support for major national strategic plans and the scientific formulation of policies.

China conducts the census every ten years to determine population growth, movement patterns and other trends, using the findings to apportion resources for education, health, transportation, labour, elderly care and other services.

The previous tally in 2010 counted 1,339,724,852 persons, an increase of 5.83 percent, or 73,899,804 people — equal to adding more than the population of France over 10 years.