BEIJING -- Beijing starts a population sampling survey on Tuesday.

The survey is estimated to reach 600,000 registered Chinese citizens from 1,162 communities in 16 districts, said Shen Qing, an official with the Beijing municipal statistics bureau.

People polled in the survey need to tell interviewers a series of basic information such as gender, date of birth and occupation, etc.

Beijing was home to 21.7 million permanent residents by the end of 2015. It plans to cap its population at 23 million by 2020, reducing the population in six core districts to 15 percent lower than 2014 levels.

At the same time, Beijing plans to improve its population census system over the next five years, and create an electronic database with the basic information of residents.

"A complete and reliable database with timely updates could provide fundamental information for the city's development," Shen said.

China's regulations state that the country should conduct a national population census every ten years -- the latest was in 2010. The country samples about one percent of its population in two rounds of population surveys.