Census takers register residents' information of a household in Qidong Village of Qicun Town, Zaozhuang City of east China's Shandong Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country. (Photos: Xinhua)

Census takers register residents' information of a household in Zipeng Town of Feixi County, Hefei City of east China's Anhui Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

Census takers register residents' information of a household in Zipeng Town of Feixi County, Hefei City of east China's Anhui Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

Census takers register a resident's information via an electronic device at a community of Suqian City, east China's Jiangsu Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

A census taker registers a resident's information at a community of economic development zone of Yantai, east China's Shandong Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country. (Photo by Sun Wentan/Xinhua)

Census takers register residents' information of a household in Qidong Village of Qicun Town, Zaozhuang City of east China's Shandong Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

A census taker updates the latest progress information at a community of Lianyungang, east China's Jiangsu Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

Census taker Li Sha (C) registers a resident's information via cellphone at a community of Lianyungang, east China's Jiangsu Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

A census taker and an instructor register residents' information of a household in Qianxi County of Bijie, southwest China's Guizhou Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

Census takers pose for photos at a community of Huai'an, east China's Jiangsu Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

A resident signs as a census taker and an instructor register his information in Baokang County of Xiangyang, central China's Hubei Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.

Census takers and instructors arrive at a community to register residents' information in Qianxi County of Bijie, southwest China's Guizhou Province, Nov. 1, 2020. China on Sunday started its seventh national population count, with about 7 million census takers going door to door to document demographic changes in the world's most populous country.