According to a report by the government-backed Chinese Academy of Social Sciences (CASS), skewed gender ratio led by sex-specific abortions will pose serious problems for the 1.3 billion population in China by 2020.
More inter-generational marriages with wives being older than their husbands' will emerge due to a large proportion of men born since the 1980s, the report said.
Despite being illegal, sex-selection services for non-medical reasons are still available and affordable in China, the academy said.
"The problem is more serious in rural areas due to the lack of a social security system there," Wang Guangzhou, a researcher at the academy was quoted by the Global Times as saying.
According to the country's National Population and Family Planning Commission, a normal sex ratio at birth, or SRB, ranges from 103 to 107 males for every 100 females.
China introduced a one-child policy in 1979 and imposed restrictions on family size. It encouraged late marriages and childbearing and this is believed to have contributed to the gender imbalance.