Almost half the 1.34 billion-strong population – 49.7% – now live in cities, compared with just a fifth when economic reforms began in earnest in 1982. The finding is among the results of the largest ever population-counting exercise in the world: a project so vast it required 6 million census takers.
Although the annual average growth rate has slowed since the last survey was taken, from 1.07% to 0.5%, China still added more than 73.9 million people over the decade: more than the entire population of the UK.
The figures, released today by the National Bureau of Statistics, underline the enormous challenges facing a country with a rapidly ageing population and huge demographic shifts. They also highlight arguments about the need to reform the country's strict one-child birth control policies.
The number of young people fell sharply as a proportion of the population, with under-14s accounting for just 16.6% of the population, down 6.3 percentage points from 2000. Meanwhile, the number of people over 60 rose by nearly three percentage points, to 13.3% of the total population.
China must now sustain the remarkable development that has made it the world's second largest economy with a shrinking workforce and growing number of dependents.
Officials believe that without the strict one-child policy – which actually allows many in the countryside and some in the cities to have two children – the population would have grown by an extra 400 million people over the last three decades. But it was only supposed to last for 30 years and many now believe the country needs to move towards a uniform two-child policy, to tackle the issue of ageing and perceptions of unfairness.
In a meeting of senior leaders ahead of the release of the figures, China's president, Hu Jintao, said the country should adhere to the basic state policy of family planning, maintain a low birth rate and deal with its population problems, the state news agency Xinhua reported.
Although some read that as a repudiation of change, others saw it as a public acknowledgement of debates on how to manage family planning. The remarks do not rule out changes to the rules, which would almost certainly be made gradually because officials fear that abrupt shifts could cause an enormous boom in births. The authorities have gradually introduced a series of exemptions in recent years.
Wang Feng, a population expert and director of the Brookings-Tsinghua Centre for Public Policy in Beijing, told the Associated Press that Hu's comments were "highly significant". "I take this as an important signal that the debate has reached a high level and that changes will be on the way," he said.
Ma Jiantang, commissioner of the National Bureau of Statistics, said his understanding of Hu's speech was that China "needed to follow closely the new situation and changes. On this basis we will have further studies and research on the rules."
The one-child policy has also contributed to the large gap between male and female births, although experts believe other factors play a bigger role: India, which has no such policies, has a similar disparity. Ma said the number of excess male births was slightly higher in 2010 than 2000, with 118.06 boys to every 100 girls, up from 116 to every 100. But the trend was unclear, with a 2009 sampling showing 119.45 boys to every 100 girls.
"We take the challenges reflected in this figure very seriously and will adopt more effective measures including promoting gender equality and equal remnuneration ... We are confident the ratio will gradually move towards a normal one," he said.
Ma thanked all those involved in the mammoth effort to enumerate the population and "in particular those comrades who sacrificed their lives for the census".
"They will forever stay with us and we will forever remember them," he said.
The bureau said the deaths were "mostly due to health and working issues" but did not give any further details.
Other figures issued on Thursday indicate striking social changes. The average household has shrunk from 3.44 people to 3.1, thanks to an increasing tendency for young couples to live alone – rather than with parents – as well as declining fertility and rising migration.
The number of migrants living outside their registered township rose by more than 100 million, to 221 million, in the last decade, the figures showed. The astonishing expansion in higher education is also documented. In 2000, 3,611 people in every 100,000 had been to university; by last year that had more than doubled to 8,930.