The first number everyone wanted to know from China’s 2010 census was the TFR — Total Fertility Rate. The second is the SRB — Sex Ratio at Birth.
The Chinese have been practicing sex-selective feticide on a large scale since cheap prenatal ultrasound scanning became available in the early 1980s. Given the cultural preference for male children, the result has been an excess of males, the oldest demographic cohorts affected being now in their late twenties.
The TFR and the SRB interact in an interesting way. Chinese statistics should always be viewed with suspicion, but we have good-quality data from other countries with the same problem, notably South Korea. What this data tells us is that the SRB for first births is normal almost everywhere. It’s in second and subsequent births that the imbalance shows up.
For South Korea in 1992, for example, one of the tables in this paper gives the following SRBs for first, second, third, and fourth births respectively: 106, 113, 196, 229. (I.e. 106 male babies per 100 female, etc. Note: An SRB of 105 is normal for north-Eurasian populations. Ma Nature knows that males are less likely to make it to childbearing age.)
It follows that as TFR drops, the SRB trends back to normal. This in fact seems to have happened in South Korea, where the SRB is indeed almost normal now, after decades of imbalance. It’s normal because South Korea’s TFR is around 1.2. When hardly anyone is having a second-or-subsequent child, unbalanced SRBs in that zone hardly matter!
You may be thinking that since China has a one-child policy, it ought to have a nearly-normal SRB. That misunderstands the policy, which for many years now has only been strictly applied in urban districts. Rural couples are allowed a second child without penalty if the first child is a girl; and with rising personal income the penalties have anyway become manageable for great numbers of Chinese people. That is not even to mention the fact that after 62 years under communism, with 2,200 years of bureaucratic despotism preceding that, the Chinese are Olympic-class gamers of the system. The paper I linked to above shows the following SRBs for first, second, third, and fourth births respectively in 2001 China: 106, 124, 128, 131.
There is some speculation about what the social and political effects of the male surplus will be. Some writers have argued that it will have national-security implications for the U.S.A. I say fiddlesticks. It’s been the case in societies all over, all through history, that there were not enough brides for the available men. This was certainly so in China because of polygamy. A dear old friend of mine, recently deceased, was born in Guangdong Province in the late 1920s to a father with seven wives. (And this, note, in a nation where female infanticide was still in play, as it had been among the poorer class of peasants since time immemorial.)
Even in monogamous cultures there have been adult sex-ratio imbalances due to such factors as male deaths in war and vendetta, and the shunting off of high-status females to convents. If there’s any good data showing that popualtions with surplus males are more prone to warfare or despotism than those without, I’d like to see it. As Mara Hvistendahl notes in her forthcoming book on the subject, “Adolf Hitler came to power at a time when Germany had over 2 million more women than men as a result of the toll taken by World War I.”
So what’s the mystery number, China’s 2010 SRB? Looks like 118. Google News “china census” for more details and some different opinions. If 118 is right, that’s a slight falling-off from the middle of the decade, probably just due to declining TFR on the South Korean pattern.