Sex Selection Shocker

Amartya Sen wrote his famous piece on systematic gender bias, provocatively titled "More Than 100 Million Women are Missing," nearly 18 years ago. Since then, a great deal of work has looked at the causes of the pro-male sex ratio seen in many parts of the world, particularly Asia. Even so, it is a phenomenon we do not understand well and the problem has certainly not gone away. Indeed, two of the largest offenders, India (the North mainly) and China, appear to be going strong with these practices, likely driven by the diffusion of technology allowing prenatal sex determination.

Despite widespread prevalence of pro-male sex ratios, and being brought to attention about these sad demographic curiosities nearly two decades ago, I always seemed to be shocked by the latest statistic on gender bias. A recent paper by Douglas Almond and Lena Edlund, published in the Proceedings of the National Academy of Sciences, literally made me fall out of my chair. Here's the punchline:

We document male-biased sex ratios among U.S.-born children of Chinese, Korean, and Asian Indian parents in the 2000 U.S. Census. This male bias is particularly evident for third children: If there was no previous son, sons outnumbered daughters by 50%. By contrast, the sex ratios of eldest and younger children with an older brother were both within the range of the biologically normal, as were White offspring sex ratios (irrespective of the elder siblings' sex). We interpret the found deviation in favor of sons to be evidence of sex selection, most likely at the prenatal stage.

Of course, nobody should be surprised that this involves Asian parents. But this is happening in the United States and the data comes from the 2000 Census. Wow. I truly hope Almond and Edlund are working on a follow up to characterize what exactly is going on here: obviously abortion is a hush-hush topic, but it is hard for me to imagine Asian parents in the United States (whatever flavor) deliberately getting one in order to avoid a having a girl.

Also, I wonder if this bias is apparent among live births, as well. That is, within families, to parents (especially the Asian kind) systematically favor boys over girls? I am not sure a U.S. sample survey with large enough numbers of Asian families and child-by-child measures of parental investments is available (perhaps the CPS?) for analysis. But I would be interested to see some results if there is data out there.

Finally, gender bias is not restricted to Asian families. An intriguing paper by Enrico Moretti and Gordon Dahl finds the following results for the United States:

This paper shows how parental preferences for sons versus daughters affect divorce, child custody, marriage, shotgun marriage when the sex of the child is known before birth, and fertility stopping rules. We document that parents with girls are significantly more likely to be divorced, that divorced fathers are more likely to have custody of their sons, and that women with only girls are substantially more likely to have never been married. Perhaps the most striking evidence comes from the analysis of shotgun marriages. Among those who have an ultrasound test during their pregnancy, mothers carrying a boy are more likely to be married at delivery. When we turn to fertility, we find that in families with at least two children, the probability of having another child is higher for all-girl families than all-boy families. This preference for sons seems to be largely driven by fathers, with men reporting they would rather have a boy by more than a two to one margin. In the final part of the paper, we compare the effects for the U.S. to five developing countries.