In India, the practice of aborting female fetuses increases as women become better educated and wealthier, defying the predicted decline of a widespread cultural preference for sons.
And as many as 12 million girls have gone "missing" from the population since 1985 because of the practice, according to new research released Tuesday by the leading medical journal The Lancet.
"There is really no change in stated son preference over the last 10 to 15 years," said Prabhat Jha, an epidemiologist at the University of Toronto who led the study. "Fertility has dropped substantially due to economic growth and increases in literacy, which are all very good things, but that has also meant that ultrasound use and access is increasing. Families appear to be saying, 'If nature – or God, if they're religious – gives us a first boy, then we will have one more child and that's it, but if we have a first girl we will use ultrasound [and abortion]to ensure our second and last child is a boy.' "
Recently released data mean he and colleagues are able to study the trends since 1985, when ultrasound gender testing was introduced here. "And it isn't slowing down."
The researchers used census data, and 265,000 birth histories collected in India's National Family Health Survey, to estimate differences in the girl-boy ratio for second births in families in which the first-born child had been a girl. They found that the girl-boy ratio fell from 906 girls per 1,000 boys in 1990 to 836 in 2005.
But in cases where the first child born was a boy, there was no drop in the girl-boy ratio for the second child: evidence that parents are selectively aborting girls if their first-born child is a girl, Dr. Jha said.
This difference in the ratio of girls to boys born was much sharper in mothers with 10 or more years of education than in mothers with no education; the difference is also greater in better-off households compared with poorer ones.
The study says that there is not yet clear evidence of the selective abortion of first-born female fetuses, as is common in China, where son preference is also strong and where state policy restricts families to only one child. But that may come as growing numbers of families choose to have only one child, particularly in urban areas.
Dr. Jha, who directs the U of T's Centre for Global Health Research, said the study makes clear that the steps taken by the government to end sex-selective abortion have not been successful. The law banning prenatal sex determination is a good one, he said, but the private health-care sector in India is so minimally regulated that the law has had little impact.
To calculate the number of female fetuses aborted for sex selection since the introduction of ultrasound gender determination in 1985, the authors calculated the expected number of births of girls, based on the ratio of 950-975 girls born to 1,000 boys in societies without son preference, and compared it against the actual number of births of girls enumerated by the censuses, done every 10 years.
After adjusting for excess mortality rates in girls, the authors estimated that there were between zero and two million selective abortions of girls from about 1985 to 1990; 1.2 million to 4.1 million in the 1990s, and 3.1 million to six million in the 2000s – for a total of between four million and 12 million by 2010.
Before the release of 2011 census data last month, there was speculation here that rising income levels and education levels for women, combined with public education campaigns and efforts at enforcement by government over the past 15 years, would show a slowing of sex-selective abortion.
"I was quite surprised that the ratios had gone down further," said Dr. Jha, who has worked on this subject for a number of years.
In an interview in Delhi, he noted, sounding rueful, that he and his colleagues "can't really explain why" son preference is persisting with such dramatic consequences, as they were not studying causes. Analysts in the Indian media frequently cite the practice of paying dowry for brides, which has been illegal for decades but is still widespread, as one possible explanation.
A further finding of the research is that a majority of Indians now live in states where selective abortion of girls is common. Until this year's census data, which showed a decline in sex ratios in a majority of states, it had been believed that the practice was largely confined to a handful of states with deeply rooted cultural aversions to female children.