Young men apply for a matchmaking program in Binzhou, Shandong province, on Aug 2. China will continue to experience a gender imbalance with more single men than women. [Guo Zhihua / For China Daily]

China may fail to curb its worrying gender imbalance before 2015 as planned, the country's top family planning body said.

The Sixth National Population Census showed that every year, there were about 1.2 million more "leftover men" — men who are above 30 years of age and unmarried.

By 2020, China will have at least 30 million more unmarried men than women between the ages of 20 and 45.

"It is a grave social problem as many men will face old age without the economic and emotional support of a family," said Zhai Zhenwu, head of the School of Social and Population Studies at Renmin University of China.

To curb the skewed birth sex ratio, the National Health and Family Planning Commission launched a five-year plan to drop the ratio to 115 male newborns for every 100 females by 2015. The current ratio is 117.6 to 100.

Li Bin, minister of the commission, addressed the difficulties and her worries about achieving the goal during a conference in late July.

The international average, which was believed to be the least harmless for the development of society, is roughly 103-107 to 100.

Lu Huajie, a professor of sociology at Peking University, expressed pessimism.

"According to the National Bureau of Statistics, the sex ratio at birth of past four years has been around 117 or 118 to 100. It has already been an impossible mission to even reach the '115 to 100' goal," he said.

Li said illegal gender testing and subsequent abortions are mainly responsible for the current situation.

Zhai said the root cause lies in a slow-changing preference for boys in rural areas.

Lisa Eklund, a sociologist from Lund University in Sweden, found that a preference for boys remains steady in rural China, while at the same time adult sons in cities have been given a more important role in providing for the social and financial security of the elderly.

Wang Xu contributed to this story.