Many of the estimated 145 million Chinese who move from the countryside to cities for more than six months of the year are hesitant to report their change of location, hoping to avoid bureaucratic measures and potential fees involved in registering a new address. The issue also impacted China's last census in 2000, as internal state control of migration first loosened. The Economist says the situation will likely lead to an undercount of the country's population, which was approximately 1.33 billion at the end of 2009.
Despite methodological approaches intended to account for migrants, the official results--to be made public in April--will no doubt be controversial, says the Economist:
"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."