In the late 1970s, a Ph.D. student named Monica Das Gupta was conducting anthropological fieldwork in Haryana, a state in the north of India. She observed something striking about families there: parents had a fervent preference for male offspring. Women who had given birth to only daughters were desperate for sons and would keep having children until they had one or two. Midwives were even paid less when a girl was born. “It’s something you notice coming from outside,” says Das Gupta, who today studies population and public health in the World Bank’s development research group. “It just leaps out at you.” Das Gupta saw that educated, independent-minded women shared this prejudice in Haryana, a state that was one of India’s richest and most developed. In fact, the bias against girls was far more pronounced there than in the poorer region in the east of India where Das Gupta was from. She decided to study the issue in Punjab, then India’s richest state, which had a high rate of female literacy and a high average age of marriage. There too the prejudice for sons flourished. Along with Haryana, Punjab had the country’s highest percentage of so-called missing girls — those aborted, killed as newborns or dead in their first few years from neglect. Here was a puzzle: Development seemed to have not only failed to help many Indian girls but to have made things worse. It is rarely good to be female anywhere in the developing world today, but in India and China the situation is dire: in those countries, more than 1.5 million fewer girls are born each year than demographics would predict, and more girls die before they turn 5 than would be expected. (In China in 2007, there were 17.3 million births — and a million missing girls.) Millions more grow up stunted, physically and intellectually, because they are denied the health care and the education that their brothers receive. Among policymakers, the conventional wisdom is that such selective brutality toward girls can be mitigated by two factors. One is development: surely the wealthier the home, the more educated the parents, the more plugged in to the modern economy, the more a family will invest in its girls. The other is focusing aid on women. The idea is that a mother who has more money, knowledge and authority in the family will direct her resources toward all her children’s health and education. She will fight for her girls. Yet these strategies — though invaluable — underestimate the complexity of the situation in certain countries. To be sure, China and India are poor. But in both nations, girls are actually more likely to be missing in richer areas than in poorer ones, and in cities than in rural areas. Having more money, a better education and (in India) belonging to a higher caste all raise the probability that a family will discriminate against its daughters. The bias against girls applies in some of the wealthiest and best-educated nations in the world, including, in recent years, South Korea, Taiwan and Singapore. It also holds among Indian immigrants in Britain and among Chinese, Indian and South Korean immigrants in the United States. In the last few years, the percentage of missing girls has been among the highest in the middle-income, high-education nations of the Caucasus: Armenia, Azerbaijan and Georgia. Nor does a rise in a woman’s autonomy or power in the family necessarily counteract prejudice against girls. Researchers at the International Food Policy Research Institute have found that while increasing women’s decision-making power would reduce discrimination against girls in some parts of South Asia, it would make things worse in the north and west of India. “When women’s power is increased,” wrote Lisa C. Smith and Elizabeth M. Byron, “they use it to favor boys.” Why should this be? A clue lies in what Das Gupta uncovered in her research in Punjab in the 1980s. At the time, it was assumed that parents in certain societies simply did not value girls. And in important ways, this was true. But Das Gupta complicated this picture. She found that it was not true that all daughters were mistreated equally. A firstborn daughter was not typically subjected to inferior treatment; she was treated like her brothers. But a subsequent daughter born to an educated mother was 2.36 times as likely to die before her fifth birthday as her siblings were to die before theirs — mainly because she was less likely to see a doctor. It turned out that a kind of economic logic was at work: with a firstborn girl, families still had plenty of chances to have a boy; but with each additional girl, the pressure to have a son increased. The effect of birth order that Das Gupta discovered has now been confirmed in subsequent studies of missing girls. What unites communities with historically high rates of discrimination against girls is a rigid patriarchal culture that makes having a son a financial and social necessity. When a daughter grows up and marries, she essentially becomes chattel in her husband’s parents’ home and has very limited contact with her natal family. Even if she earns a good living, it will be of no help to her own parents in their old age. So for parents, investing in a daughter is truly, in the Hindi expression, planting a seed in the neighbor’s garden. Sons, by contrast, provide a kind of social security. A family with only daughters will also likely lose its land when the father dies: although women can legally inherit property, in areas of north India and China, they risk ostracism or even murder if they claim what is theirs. And sons are particularly important to mothers, who acquire power and authority when they have married sons. Sons, according to Chinese custom, are also needed to care for the souls of dead ancestors. What Das Gupta discovered is that wealthier and more educated women face this same imperative to have boys as uneducated poor women — but they have smaller families, thus increasing the felt urgency of each birth. In a family that expects to have seven children, the birth of a girl is a disappointment; in a family that anticipates only two or three children, it is a tragedy. Thus development can worsen, not improve, traditional discrimination. This can happen in other ways too. With the access it brings to cutting-edge technology, development can also offer more sophisticated and easier options for exercising old-fashioned prejudice. In China and in the north and west of India, for instance, the spread of ultrasound technology, which can inform parents of the sex of their fetus, has turned a pool of missing girls into an ocean. The birth of girls has long been avoided through infanticide, which is still practiced often in China. But there are even more couples who would abort a pregnancy than would kill a newborn. Ultrasound has been advertised in India as “pay 5,000 rupees today and save 500,000 rupees tomorrow.” In both countries, it is illegal to inform parents of the sex of their fetus, and sex-selective abortion is banned. But it is practiced widely and rarely punished. Finally, because higher education and income levels generate more resources, development offers new opportunities to discriminate against living girls. After all, if people are very poor, boys and girls are necessarily deprived equally — there is little to dole out to anyone. But as parents gain the tools to help their children survive and thrive (and indeed, all children do better as their parents’ education and income levels advance), they allocate advantages like doctor visits to boys and firstborn girls, leaving subsequent daughters behind. To be sure, development can eventually lead to more equal treatment for girls: South Korea’s birth ratios are now approaching normality. But policymakers need to realize that this type of development works slowly and mainly indirectly, by softening a son-centered culture. The solution is not to abandon development or to stop providing, say, microcredit to women. But these efforts should be joined by an awareness of the unintended consequences of development and by efforts, aimed at parents, to weaken the cultural preference for sons. The lesson here is subtle but critical: Development brings about immense and valuable cultural change — much of it swiftly — but it doesn’t necessarily change all aspects of a culture at the same rate. (India and China have myriad laws outlawing discrimination against girls that are widely ignored. And how to explain the persistence of missing girls among Asian immigrants in America?) In the short and medium terms, the resulting clashes between modern capabilities and old prejudices can make some aspects of life worse before they make them better. Tina Rosenberg is a contributing writer for the Times magazine.