The census is expected to confirm China's population at about 1.4 billion
By Damian Grammaticas
BBC News, Beijing
China's 2010 census will involve visiting about 400 million homes, recording the lives of 1.4 billion people an,d when it is complete, will reveal more about the powerful social forces that are reshaping the nation.
Ten o'clock on Monday morning and there is a knock at Mr Yuan's door. The 63-year-old opened up and so began the mammoth task of counting every single one of China's people.
All across this vast country, from its western deserts to its high Himalayan mountains, from its sub-tropical south to the massive industrial cities lining its giant river deltas, teams of census workers are now knocking on every door, recording every individual.
Like many things about China the scale can seem overwhelming. If you tried to count from one all to way to 1.4 billion. One, two, three and so on, it might take, very roughly, 100 years to do it.
The final census results are due to be published in December 2011
The census takers have 10 days to complete their job. But this is a country that is geared to mobilising for these huge tasks. So the solution China has come up with is to recruit six million census workers.
Mr Yuan sat at his dining table, politely answering all the questions put to him.
He was born in 1937, worked as a teacher, has one daughter, and one grandchild, they all share the same apartment. For just this one family, the census form took half an hour to complete.
Also being recorded are people's levels of education, their sources of income, their ethnic background. But some questions are not being asked, like people's religion or how much they earn.
Many in China have seen revolution, war, purges, crackdowns and labour camps. The census-takers believe that if they delve too deeply then Chinese people, suspicious of giving the state too much information about their private affairs, would refuse to co-operate.
The pace and scale of China's urbanisation exceed those of any society in human history
For China's government, the census is also part propaganda exercise. As foreign media we were only allowed to follow the census takers to Mr Yuan's apartment and one other.
Both were in a clean, new housing development in north-western Beijing. Outside children played in a schoolyard full of colourful new slides and swings.
Inside Mr Yuan's flat, 26 floors up, tropical fish swam lazily in a giant fish tank, a huge flat-screen television stood in the living room. Beijing stretched far into the distance.
Mr Yuan's family are, clearly, beneficiaries of China's economic boom.
It is a boom driven by China's massive pool of cheap workers.
Mr Liu hopes the census will change attitudes towards migrant workers
In the past two decades perhaps 200 million migrant labourers have left the countryside, pouring into the cities, looking for work on construction sites, in factories, offices and homes. Another 300 million will follow in the next two decades.
The pace and scale of China's urbanisation exceed those of any society in human history. Keeping track of this vast movement of people is perhaps the most important part of the census. And it matters because migration is an extremely sensitive issue in China.
The migrant workers do not have permanent residence rights in the cities, their access to free healthcare and education is restricted unless they return to their villages.
They are second-class citizens in the vast urban sprawls they are building. But for the first time they are going to be counted where they work. So we will get a clear picture of the way China is changing.
And it may spur the government to give China's workers greater freedoms to move and live where they like.
On Beijing's western edge we found teams of labourers welding the steel bars that will form the foundations of yet another block of flats.
Thirty-five-year-old Mr Liu from Sichuan in the south, sweat dripping from his brow said he was delighted.
"China needs to know how many people live in its cities," he said. "We should be given official residence here. Without it the police cause problems for us."
Second child penalty
Another group the government wants to count in the census is the extra children born in defiance of the one child policy.
Persuading parents to register additional children could be challenging
In his home in Beijing, David He entertained us by playing piano duets with his 12-year-old daughter Le Ran.
Playing on the floor with a toy police car was his 18-month-old son Yi Ran.
Yi Ran does not officially exist in China. He has no legal papers, which means no right to attend school or even to travel by plane.
His mother, who worked for a state-owned company was sacked from her job for having a second child.
The fine they would have to pay to register him is $30,000 (£20,000) But there is a discount if the family come forward during the census.
"We can't afford the penalty," says his father David, "but I guess we will have to register him one day or he will have problems for the rest of his life."
In a few days, the census-takers will finish counting China.
Then the stories of Mr Yuan the homeowner, Mr Liu the labourer, and the He family will combine to give us a new picture of this nation, of the vast changes happening here, and the way they are shaping a billion separate lives.
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