Timeline | 40 years of China's population policy

China on Monday relaxed its two-child policy to allow couples to have three children, a shift aimed at tackling an ageing society.

Here is a timeline of the country's evolving family planning policy.

In 1979, China imposed a policy forcing couples to have only one baby, introduced by top leader Deng Xiaoping to curb population growth and boost economic development.

The population stood at 969 million that year, a sharp increase from around 540 million in 1949.

The decades under this family planning move led to under-reporting of female births, as well as a high rate of abortions of female foetuses, skewing the sex ratio.

But the results were dramatic, with fertility rates falling from 5.9 births per woman in 1970 to about 1.6 in the late 1990s.

The government said the policy prevented about 400 million births.

Also read: China says each couple can have three children, in change of policy

Despite concerns about demographic imbalance, Chinese leaders hesitated to simply abolish the one-child policy.

Instead, since 2013, they loosened the single child rule and allowed couples where one was an only child to have a second offspring.

The population hovered around 1.36 billion at the time, according to World Bank data.

But only 1.45 million couples, or below 15 percent of those eligible, applied to have a second child as of May 2015.

Since 2016, Beijing allowed families to have two children as fears mushroomed about China's shrinking workforce.

But experts warned there would be no quick fix to the demographic challenges after strict and sometimes brutal enforcement of the single child policy.

Last year, there were around 12 million births, the lowest number since 1961.

A census released this month showed China's population grew at the lowest pace in decades, reaching 1.41 billion.

The country still has 34.9 million more men than women, making up just over 51.24 percent of the population.

Meanwhile, the number of people aged between 15 and 59 dropped nearly seven percentage points, while those over 60 was up more than five percentage points.

On Monday, in a meeting of China's elite Politburo leadership committee hosted by President Xi Jinping, officials relaxed the childbirth policy further to let parents have three children.