As part of the country's sixth national census, which began on Monday, 100,000 census takers are knocking on doors in Beijing. They have 10 days to complete their task.

?A census taker (R) surveys a housewife on Monday in Taizhou, East China's Jiangsu province. [Photo/Xinhua]

"Time is limited and the workload is huge," said Sun Shuzhen, deputy director of the census office in Dongcheng district.

The exercise will involve 6 million door-to-door census takers visiting 400 million households, including foreigners and people from Hong Kong, Taiwan, and Macao who live on the mainland.

The once-in-a-decade census will form the basis for policy-making in the world's most populous country, estimated last year to have over 1.3 billion people.

China's last census in 2000 showed the population at 1.295 billion, compared to 594 million when the first census was conducted in 1953.

Feng Nailin, director-general of the department of population and employment statistics of the National Bureau of Statistics, told China Daily that foreigners living illegally in the country will not be repatriated as a result of information collected during the census.

According to the regulation on population census, all personal information collected in the census is strictly confidential and will be handed in directly to the bureau for data processing, Feng said.

Sun said that international communities in Beijing have recruited census takers who speak foreign languages, such as English, Korean and German, or have enlisted translators to work with them.

In Guangzhou, capital of south Guangdong province, the local census office said the job will be more complicated given the rising number of foreign residents.

It has been reported that nearly 200,000 Africans live in Guangzhou, including those who have outstayed their visas or have entered the country illegally.

Since people are more likely to be at home in the evening and on the weekend, the census takers will work until 9 pm, Sun said. If necessary, they will make return visits until they manage to see the occupants.

Yang Chao, a census taker in Dongcheng district, Beijing, started work with a colleague early on Monday morning. They are responsible for interviewing 200 houses in the area.

"Our daily workload is not definite because we only know the number of households, not the number of residents in each family," Yang said.

At a 60-year-old courtyard in the Jingshan area, which is home to 13 families, Yang began by showing them a letter of intent, which states that all information collected in the census is confidential and will not be used for any other purpose. Most of the residents seemed eager to help.

"We believe the information will be used for the country to form policy, so we are willing to answer the questions," said resident Lu Fengli, who showed the family's residency card to the census takers and explained the personal situation of everyone listed on the document.

Of the long and short forms used in the census, Lu's family filled in the short one, which has 18 questions.

Ten percent of the population will be randomly selected to complete a long form containing 45 items, such as health, employment and housing conditions.

Expats will fill in a form with eight questions, while people from Hong Kong, Macao and Taiwan will answer 11 questions, including the purpose of their visit and educational background.