China's working-age population continued to fall in 2014, the government said Tuesday, as Beijing struggles to address a spiralling demographic challenge made worse by its one-child policy.

Mainland China's total population stood at 1.37 billion at the end of 2014, according to the National Bureau of Statistics, an increase of 7.1 million over the end of 2013. It remains the world's largest, although India has been catching up in recent years.

The working-age population -- which China defines as those between the ages of 16 and 59 -- dropped to 915.8 million last year, the NBS said, down 3.7 million from the end of 2013.

The population aged 60 and over, by contrast, rose by more than 10 million to 212.4 million, or 15.5 percent of the total population.

Projections show that one in four of the population -- or 350 million Chinese -- will be aged 60 or older by 2030, compared with just five percent as late as 1982.

China introduced its controversial family planning policies, which limit most couples to only one offspring, in the late 1970s in an effort to rein in population growth.

But an ageing -- and increasingly male -- populace is now starting to pose fundamental demographic challenges that officials have been trying to address.

The ruling Communist Party moved to relax the rules in late 2013 to allow couples to have two offspring so long as at least one of the parents is an only child. Yet far fewer couples have applied to have a second child than expected.

Nearly 116 boys were born for every 100 girls in 2014, while the sex ratio in the total population was 105 men to 100 women.

China's migrant population has swelled by eight million in the past year to 253 million, the NBS said.

China also released its official Gini coefficient -- a key inequality statistic -- for 2014 on Tuesday.

The figure is a commonly used measure of income inequality, with 0 representing perfect equality and 1 total inequality. Some academics view 0.40 as a warning line.

Beijing did not release the figure for several years before resuming two years ago. In 2014 it declined to 0.469, the NBS said, from 0.473 in 2013.

China's wealth gap and population imbalances are major concerns for the ruling Communist Party, which places huge importance on preserving social stability to avoid any challenge to its grasp on power.