When those charged with carrying out history's largest census arrive in this squalid migrant labourers' settlement south of Beijing, they may find it hard to get an accurate count of anything.
The muddy alleyways off Laosanyu Road teem with thousands of men, women and children, all of them from somewhere else, usually the country's vast and largely impoverished rural interior. Many have lived in and around Beijing for years or even decades; others count their time here in months or days.
The "farmer-workers," as they are known in Chinese, are at once the engine of this country's rapid economic growth, and those it has left behind. And no one knows for certain just how many of them there are.
More than six million people - a number almost three times the size of the People's Liberation Army, and larger than the population of Denmark - will on Monday fan out across this country's 31 provinces to begin China's first national census in a decade. Though a population survey carried out at the end of last year estimated the population of the People's Republic of China at 1.334 billion, there are far too many unknowns for that number to be considered definitive. Some demographers believe the real number of Chinese may be closer to 1.5 billion.
There are several reasons China's government has a poor handle on the number of people it rules, but the biggest one is that the country is in the midst of the world's biggest-ever peacetime migration. Over the past three decades, hundreds of millions of rural Chinese have flocked to the cities in search of work and better lives. Estimates of the number of migrant workers and their families range from 130 million to more than 200 million. To find the real number will mean going door-to-door in villages such as Daxing, and asking those who live here to tell the truth, even when it could have uncertain consequences.
"The number of people living here changes all the time," said Xu Yingyun, who is raising her six-year-old grandson in two small rooms the family rents at the end of one of Daxing's many alleys. She said the family had no idea who their neighbours currently are, since the other residents frequently change, with many staying only as long as their latest job lasts before moving on to another district or city.
The numbers are imprecise because China's hukou household registration system restricts where people can live and work, forcing migrants to live in the shadows of places such as Beijing, Shanghai and Guangzhou. An unknown number - believed to be in the millions - have had second or third children in violation of the country's once-child population control laws. While their parents are registered in the wrong place, the children often aren't registered at all, leaving them without the necessary documentation to even attend school.
Hoping to remove the asterisk that has long accompanied their country's population counts, China's government plans to marry a physical head count with their own population registry for the first time, with the in-person count taking precedence wherever there is a conflict. To encourage migrants to be honest about how and where they live, the government has mixed a massive propaganda campaign - green banners around the country urge citizens to "co-operate fully to reconcile household and population records" - with a promise of reduced fines for those who admit hukou violations or reveal their extra children to the census-takers.
"Our enumerators will go anywhere that there are people to register," said Fang Nailin, the vice-director of the census. "Within each block, we will not miss any building. Within each building, we will not miss any household. Within each household, we will not miss any individual. And with each individual, we will make sure they fill out each item [on the census questionnaire]"
Many Chinese scoff at such statements. The grandmothers who know the alleys of Daxing best say there's no way that migrants are going to voluntarily admit the real number of children they have when it could mean fines or worse. Company bosses in Beijing laugh about the employees they have who live and sleep where they work, and wonder how any census-taker is going to know where to look.
In an online poll on the popular sina.com website, one-third of respondents said they weren't comfortable letting census-takers into their homes.
In particular, winning trust among a migrant population that feels persecuted and discriminated against won't be easy. The answers you get from those living on the outskirts of Beijing can be evasive, and sometimes change with repeated asking: One labourer says he lives in Daxing with six family members. Half an hour later he says the real number is five, because one of his daughters recently moved to nearby Hebei province. The landlord of the same building - really just another alleyway with families behind each door - professes not to know whether it's four families or five that live in his rooms.
Even if everything goes the way the ruling Communist Party plans it, Mr. Fang acknowledged there is a margin of error to any survey of this size. And at plus or minus 1.8 per cent in the last census, there's room for an "oops" of 25 million people either way.
China's censuses were once simpler affairs. Those taken in 1953, 1964 and 1982 are seen as extremely accurate because of the level of control the government then exerted over its citizens. But the opening up of the country's economy gave birth not only to new wealth and massive migration, but also a sense of both privacy and of the value of time. "Now time is money for people. They tell us 'I don't have time to talk to you.' There's also a sense of privacy, as in 'Why are you asking me such questions?' " said Zhai Zhenwu, the director of the School of Sociology and Population Studies at Renmin University and a member of the nine-person committee that designed the census. The 1.8-per-cent margin of error in the 2000 census was 30 times that of the 1982 count, he said.
Those running the head count have noble intentions. The questions were designed, they say, to help the central government get a better hold on where people really live, what their economic conditions are and how many children in each area need to go to school.
The social policy implications for China's leaders are as staggering as the numbers. If there are many million more people than previous believed, and if most of those extra citizens are living on the fringes of society in China's cities, then the argument to reform the country's hukou registration system - which condemns migrants to society's margins by denying them access to public services outside of their registered hometowns - becomes that much more compelling.
The census will also likely give more ammunition to opponents of the country's controversial one-child policy - which has been thrust unfavourably back into the limelight in recent weeks by the story of a woman in the southern city of Xiamen, eight months pregnant with her second child, who was forced by officials to have an abortion.
Prof. Zhai said another key goal of the census is to get a more accurate picture of the country's income gap, which has expanded dramatically over the past two decades. According to the government's own figures, the Gini coefficient, which is used to measure income inequality, a decade ago passed 0.4, historic danger point for triggering instability, and now stands at 0.47. "If the census shows that the Gini coefficient is bigger [than expected] the government needs to put more effort into solving the problem. But if it shows the number is still bearable, then we can continue our current policies," Prof. Zhai said.
The head count will also reveal again how fast China is aging. One-fifth of the population is expected to be 65 or older by 2020, potentially making China the first country to grow old before it grows rich, and putting an enormous burden on those single children as their parents' generation retires. It seems inevitable that new census data will force the government - which is cash-rich but presides over a torn social security net - to consider new investments in public health care and a national pension program.
Getting those policies right, of course, relies on the army of census-takers getting the numbers right this time around. But many in Daxing say they're not sure they'll be around when the enumerators come asking their questions.
"This is an important national project," said Han Jiuren, a 49-year-old home decorator who lives in Daxing but is registered in another province. "But I might not be home that day."
Asking the basics
China's 2010 Census - short form
2. Relation to head of household
4. Birth date
6. Residence at time of census
7. Permanent registered address (hukou):
8. Period of time since left permanent registered (hukou) address,
9. Reason for leaving
10. Type of hukou (urban/rural)
11. Literate or illiterate?
12. Highest level of education
13. How many people stayed at current address the night of Oct. 30?
14. How many the night of Oct. 31?
15. Number of births in household in past year
16. Number of deaths in household in past year
17. Size of living area
18. Number of rooms
China's census, by the numbers
1953: 594 million
1964: 694 million
1982: 1.01 billion
1990: 1.13 billion
2000: 1.26 billion
2009 (estimate based on survey): 1.33 billion
90 per cent will get a short-form survey with 18 questions
10 per cent will get a longer-form with 45 questions
5 million enumerators, or one per "census block" of 250-300 people
1 million instructors and supervisors
50 per cent are civil servants borrowed from their departments
50 per cent are being paid for their time
20 government agencies are involved
Field work begins Nov. 1 and lasts until Nov. 20
Processing and analyzing begins Dec. 1 and lasts until December 2011
Preliminary results will be released in April 2011
Total cost estimated at 8 billion yuan, of which central government in Beijing has agreed to pay 1.3 billion yuan
The Great Migration:
Percentage of China's population living in cities:
1978: 18 per cent
1989: 26 per cent
1997: 32 per cent
2002: 39 per cent
2008: 46 per cent
2010: More than 50 per cent (expected)
The income gap:
Factor by which income of top 10 per cent exceeds that of bottom 10 per cent
Sources: China's National Bureau of Statistics; Xinhua news agency; The State of China Atlas, c 2005, 2008, University of California Press