Beijing, Nov 1 : China on Sunday kicked off its seventh national population census, with about 7 million staff to visit homes for registration work. 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 at a video conference to promote the national census. 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. The sixth national population census, conducted on November 1, 2010, had revealed that the total population of mainland China was 1,339,724,852, an increase of 73,899,804 from the previous one conducted in 2000, representing a growth rate of 5.84 per cent over the decade. /IANS