For more than thirty years, the Chinese government has been carrying out one of the most massive social experiments in human history. In order to head off what officials believed to be an unsustainable rate of population growth, it enacted, and has often brutally enforced, a one-child policy. While the policy has slowed population growth in China, the side effect has been the creation of an unprecedented gender imbalance.

Ever since the early 1980s, when ultrasound examinations became widely available in China, the number of boy births per 100 girl births has soared. According to China’s National Bureau of Statistics, it reached a peak of 120 in 2008. Although that number dropped to 117 in 2012, it still remains well above the normal range of 103 to 107.

The government has gradually loosened this policy over the last few years by allowing couples to have a second child in certain circumstances, but these changes will not untie China’s current demographic knot—a knot brought about by thirty years of sex-selective abortions.

The skewed gender ratio in China has created a generation of young men without hope of finding a mate. The social consequences of this phenomenon are just beginning to be realized. Columbia University economist Lena Edlund has estimated that for every 1 percent increase in the gender imbalance, there is a 6 percent increase in violent crime and property crime. Too many young men deprived of the stabilizing influence of family life and familial responsibilities spell trouble for a society. With a rising number of unpaired males, it is not surprising that high-risk male-associated crimes such as gambling, drug abuse, and female trafficking are on the rise in China.

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Could such a problem occur here? While there currently is no danger that our government will enact a one-child policy, Americans are already voluntarily inflicting such a policy on themselves. In 2012, the US fertility rate fell to a record low, with 63 live births per 1000 women of child-bearing age. To maintain the US population at a stable level, a birthrate of 2.1 children per woman is necessary. The US has been below that number for years and is trending downward. In fact, the Centers for Disease Control and Prevention report that the US’s total birthrate has fallen to a record low of 1.88. This puts the US behind both France and England.

While the US birthrate is significantly above the estimated Chinese birthrate of 1.5, it is creeping into dangerous territory. Demographers consistently warn that below-replacement birthrates are problematic for Western societies, given the dearth of young workers that will be available to fund Social Security and Medicare programs for the elderly.

Japan, for example, has roughly 40 elderly people for every 100 working-age adults. That number is projected to jump to near 60 by the year 2030. The US currently sits at 23.9 seniors for every 100 adults ages 20-64, but in just eight years that number is projected to be at 30 and rising. These numbers will not be sufficient to sustain social welfare programs for the elderly at the current benefit levels.

There are other negative social effects wrought by lower birth rates, such as slower economic growth and decreased economic innovation. What is often overlooked, however, is the possible link between low birthrates and gender imbalances. If in China only one child is permitted or, in the case of the United States and many other Western countries, only one child is desired, it is possible that the same type of gender imbalance could occur. Admittedly, although a low birthrate is an important factor, it does not have a one-to-one correlation with gender imbalances. Many European countries have low birthrates but have yet to see gender-ratio disturbances.

In the case of China, its gender imbalance was facilitated by three additional factors. The first was an underlying social preference for one gender (boys). The second was the development and widespread availability of adequate technologies to allow for sex selection. The third was the social acceptance of—or at least ambivalence toward—the use of these technologies for sex selection.

As the case of China suggests, these three factors coupled with a low birthrate will lead to a gender imbalance. This is beginning to happen across Europe, as countries such as Liechtenstein, Albania, Kosovo, and San Marino have estimated birth gender ratios at or above 108.

But could this happen here? It is clear that the US birthrate is falling, but what of the other factors? When it comes to gender preference, it turns out that the Chinese are not unique. A Gallup poll, administered ten times since 1941, has consistently found that Americans have a preference for boys as well. When Americans are asked whether they would prefer a boy or a girl if they could only have one child, there is a 10-15 percent higher preference for a boy. If widely acted on, this bias is enough to skew the gender ratio into dangerous territory.

Of course, if Americans continue to have an average of two kids, the evidence indicates that the gender ratio will remain in stable territory. But if more and more Americans choose to have only one child, all bets are off. Indeed, increasing permissiveness toward gender selection in the US, and the development of new technologies to facilitate the process, make things look even more problematic.

Sex-selective abortion is already occurring in the US, but at present it seems to be restricted mainly to Chinese, Indian, and Korean immigrant populations. Whether this will eventually disturb the overall gender ratio—given that foreign-born women have a 50 percent higher birthrate than US-born women—is still unknown. Likewise, the effect the practice among these immigrant populations has on the general attitude of Americans toward sex-selective abortion remains to be seen. Regardless, gender selection is already happening in the West. With the advent of new techniques for pre-natal genetic testing and the rise of in vitro fertilization, the prevalence of gender selection is very likely to increase.

Currently, most couples do not know the sex of their baby until the standard pre-natal ultrasound around 16-18 weeks. However, there are now new, non-invasive pre-natal tests that can determine the sex much earlier. Using only maternal blood, which contains significant amounts of fetal DNA, the sex of the baby can be determined with 95 percent accuracy at only seven weeks.

In the past, couples desiring only one male child may have been reluctant to abort the 16-week-old baby depicted on an ultrasound. If these same couples are now able to determine the sex of the baby at 7 weeks, a point at which friends or family may not have even noticed the pregnancy, they may be more likely to pursue a sex-selective abortion in relative anonymity. Even if there is social pressure against sex-selective abortions, and polls show that over three-quarters of Americans oppose such abortions, early tests would allow the small minority of couples that are interested to proceed, insulated from the pressures of friends and family.

While the fact that most Americans oppose this practice may give one comfort, it is important to realize that it doesn’t take much to shift the gender ratio. For example, it would only take 80,000 fewer female births in the US—a number that reflects just 2 percent of all births—to shift a healthy gender ratio of 1.04 up to the problematic level of 1.08.

Yet, earlier pre-natal tests represent only one technological advance that may affect gender ratios. The increasing reliance on IVF techniques could have an even more dramatic effect on gender ratios. In 2011, IVF produced over 61,000 live-born children, a number that has nearly doubled in the last ten years and shows no signs of reversing.

More and more couples are turning to IVF clinics, and sex selection of embryos—a practice that is more widely accepted than sex-selective abortions—is becoming commonplace. While there are a number of techniques that can be used to increase the likelihood of having a boy via IVF, many clinics advertise their willingness to do pre-implantation genetic diagnosis on embryos for the purpose of sex selection.

In fact, the Ethics Committee of the American Society for Reproductive Medicine, an industry group that attempts to self-regulate IVF clinics, stated that “it would not be unethical for parents to prefer that their first-born or only child be of a particular gender because of the different meaning and companionship experience that they expect to have.”

Absent virtually any outside oversight, the IVF industry is poised to take full financial advantage of the “right to have a child of one’s gender preference.” In addition, surveys indicate that 40 percent of Americans would take advantage of pre-implantation sex selection services if offered. This indicates that such selection is quickly becoming mainstream. As the number of IVF-produced children trends upward and the overall birthrate drops, we are heading into uncharted territory.

Preventing gender selection via IVF or sex-selective abortion is not as simple as making these practices illegal. Such laws have already proven easy to circumvent in other countries. Still, laws banning gender selection can help to maintain social pressure against these practices.

It is time for the US to legally ban gender selection. We must prevent a China-like destabilizing gender imbalance from occurring here.