China has kicked off its once-a-decade census from Nov 1 to 10, with six million "census takers go door-to-door to document the massive demographic changes taking place in the world's most populous country," said an article in UK's Daily Telegraph on Nov 1.

According to China's figure in 2000, its official population reached at 1.295 billion people. "In the 10 years since, there has been an extensive shift in the population base as millions of migrant workers have poured into urban areas from the countryside."

It is the sixth time China has "carried out a national census but the first time it will count people where they live and not where their resident certificate, or hukou, is legally registered." "The change will better track the demographic changes and will reveal the true size of China's giant cities, the populations of which have up to now only been estimates."

However, "citizens' privacy concerns could be one of the biggest challenges for the census takers." After years of reforms "some Chinese may be reluctant to give up personal information, harboring suspicions about what the government plans to do with their details."

Another complicating issue is children born in violation of the family-planning policy, "many of whom are unregistered and therefore have no legal identity. They could number in the millions."