|Half of China's population now live in cities, crossing a historical landmark from a more rural past [EPA]
China's population has increased to 1.34 billion but more people are ageing, a development experts say will likely spur calls for the "one-child" policy to be relaxed.
Census data gathered in 2010 and released on Thursday showed the population in the world's second biggest economy grew by 5.84 percent from the 1.27 billion in the last census in 2000.
This level was smaller than the 1.4 billion some demographers had projected.
As China is fast urbanising and becoming older, these trends augur big changes in the labour market in coming years, the results showed.
The number of potential workers, especially from the countryside, is shrinking and the elderly dependent population is increasing.
By 2010, half of China's population, 49.7 per cent, lived in urban areas. In 2000, 36.1 per cent lived in cities and towns, although that census used a different counting method.
By 2010, 261.4 million Chinese were counted as "migrants", meaning they were residing outside of their home villages, towns or cities. Most of them are farmers from the poor inland who have moved to cities and coastal industrial zones to find work.
"What's significant is that China is for the first time crossing a historical landmark from a country that's dominated by people engaging in agriculture, living in the countryside, to an urbanised society," said Wang Feng, a demographer who is director of the Brookings Institute Tsinghua Center for Public Policy in Beijing.
"Such low fertility and population growth means that China will face a future smaller cohort of young labour for labour supply, and also a much more serious ageing process than people anticipated even 10 years ago or two decades ago."
Those rapid changes have not always been smooth, Ma Jiantang, the head of the National Bureau of Statistics, told a news conference.
"The data from this census show that our country faces some tensions and challenges regarding population, the economy and social development. First, the ageing trend is accelerating, and second the size of the mobile population is constantly expanding."
The results could encourage the government to relax family planning restrictions that limit nearly all urban couples to one child, while rural families are usually allowed two, said Du Peng, a professor at the Population and Development Studies Center at Renmin University in Beijing.
"The total population shows the general trend towards slowed population growth and as well an older population, and in the next five years or longer that will be an important basis for population policy," said Du.
"The ageing of the population appears faster than was expected."
Hu Jintao, the Chinese president, told a meeting of top Communist Party leaders convened to discuss population issues that China will maintain its strict family planning policy.
Demographers advocating changes to the one-child policy took a counterintuitive look at Hu's speech, suggesting his decision to publicly address family planning now meant there was fresh debate among the leadership about how best to manage it.
The proportion of mainland Chinese people aged 14 or younger was 16.60 per cent, down by 6.29 percentage points from the number in the 2000 census. The number aged 60 or older grew to 13.26 per cent, up 2.93 percentage points.
The figures also showed that China's population is growing more slowly than in the past. Between 1990 and 2000, the total population increased by 11.7 per cent.
China's chief statistician, Ma, acclaimed the numbers as a vindication of the government's firm, sometimes harsh, family planning policies.
"These figures have shown the trend of excessively rapid growth of China's population has been under effective control," Ma said.
But one economist said China's slowed rate of population growth and shrinking pool of migrant labour from the countryside could add to long-term pressures driving up wages and prices.
"What really matters is the one-child policy that has created a cliff-fall (in the population) in the last three decades," said Dong Tao, an economist at Credit Suisse in Hong Kong.
"That is starting to show in rural labour markets and the entire economy feels the pain as this becomes a major source of inflation," he said in a telephone interview.
The shift of the population to urban areas has put great pressure on cities like Beijing and Chongqing and will likely to spur continued high levels of infrastructure spending in coming years.
The Chinese government's strict controls on family size have brought down annual population growth to below 1 percent and the rate is projected to start falling in coming decades.