The sex ratio at birth in China began to deviate from the normal range in the early 1980s, and has continued to rise during the past three decades. Though some optimistic research studies assert that the sex ratio at birth in China has begun to decline, the 2010 census shows a sex ratio at birth of 118.06 males per 100 females for 2010, an increase when compared the sex ratio of 116.9 males per 100 females seen in the 2000 census. The cohorts born in the 1980s are now of marriageable age. For the years 2015 to 2045, the ratio of potential marriageable males to females is predicted to be over 115:100, and China will face an annual surplus of one million males who cannot find a spouse in domestic marriage market. As women tend to marry men whose socioeconomic status is equal to or higher than theirs own, it is the men from the lowest socioeconomic strata who not able to find a wife.
Source: Estimates of Missing Women in Twentieth Century China