The worlds biggest headcount

Some 6 million people in China have been mobilised to conduct a10-day survey of the worlds largest population. The census is complicated by surging numbers of migrants from rural to urban areas. Debates over the accuracy of the counts will not be laid to rest. This is Chinas sixth nationwide census as a communist country. The previous one,in 2000,was already fiendishly hard because of a loosening of controls on internal migration. Surveys suggest that since then the number of people who have moved out of the countryside and taken up urban residence for more than six months has grown by 85 per cent,to 145 million. Such people will often not tell the authorities they have moved,in order to avoid all the bureaucracy and possible costs involved in registering a new residence. Migrants are particularly fearful of revealing any children born in violation of Chinas frequently strict family-planning regulations.

Now officials are trying to convince people that personal data gathered by census takers will be kept secret,even from other government departments. Still,state media reports that many are evading the enumerators. Preliminary data are due to be released in April. The problem will be how to handle the inevitable undercounting.

In 2000 the census takers reported an undercount of 1.81 per cent. Officials deemed this to be within acceptable limits. To compensate,they added more than 22 million notional people to the total,to produce a population of 1.27 billion. Many of the uncounted were so-called black children,ie,those born in breach of regulations that limit urban couples to a single child. From sample surveys,officials estimate the population at the end of 2009 to have been 1.33 billion.

In this census,migrants will be counted both in their home town and in their new city so that figures can be cross-checked. Foreigners will be included for the first time. But academics say census data are still being moulded to fit official projections. Chinas fertility rate may be much lower than official estimates.

Motivating poorly paid enumerators to do their job properly is another problem. The same number who gathered data from 350 million households in 2000 must cover 400 million this time round. Not just migrant workers but also the new middle class dislike official prying. In Beijing some census workers have already resigned,citing the pressures.

The Economist Newspaper Limited 2010