Dollars and Sex (3 page)

It is a common misconception that birthrates within marriage began to fall only when the birth control pill became available in the 1960s. In truth, birthrates began to fall right after the onset of the Industrial Revolution over two hundred years ago as couples chose to have fewer children in response to higher wages for skilled workers (we will return to this later). Oral contraceptives may have made it easier for women to control the timing of their births, but women have found ways to control their fertility for centuries.

In the United States, for example, the average woman in 1800 had given birth to seven babies by the time she turned 40. That number fell every decade in the nineteenth century and right up until the end of the 1930s, when the average woman had given birth to only two children. So, thirty years before the pill was available on the market, birthrates had already fallen to today's low level.

Throughout most of human history, the only way to have sex and avoid pregnancy was coitus interruptus—a.k.a. withdrawal. Marrying later in life also helped to reduce a woman's childbearing years (in a time in
which extramarital childbearing was virtually unheard of) and was actively promoted by Thomas Malthus, whom I mention in the Introduction. High rates of spinsterhood also helped to lower average birthrates (and, in fact, the main contributor to the increase in children during the baby boom was not families that had four or five children, but rather the increase in women who had just one child rather than none at all). Anal sex and nonejaculation were also used to control fertility but apparently were techniques more commonly used by sex workers.

Condom use appears to go back three thousand years, but the first really useful technology to control pregnancy was the cervical cap, introduced around 1838. As we have already heard, Casanova (who lived from 1725 to 1798) had a similar idea, using lemons as a barrier, but that didn't appear to catch on to any degree (perhaps because only a man as charming as Casanova could convince a woman to insert half of a lemon into her vagina).

In the 1850s, Charles Goodyear learned how to vulcanize rubber, making possible the production of condoms that were more comfortable, fairly inexpensive, and effective at preventing pregnancy. At roughly $34 per dozen (measured relative to today's real wages), they were still expensive for frequent usage by the average worker; they were so expensive, in fact, that it was common for men to wash and reuse them.

Diaphragms became available in 1882, followed by the intrauterine device (IUD) in 1909. Latex condoms were produced in 1912, making them, thankfully, disposable and much cheaper.

SO, THE PILL IS RESPONSIBLE FOR INCREASED PROMISCUITY, RIGHT?

It seems that ever since women could predictably control their fertility, more and more women have been deciding that the benefits of having premarital sex outweigh the costs. It would be easy to argue that the availability of contraceptives, particularly the availability of the birth control pill, is directly responsible for this change in behavior if there weren't a
confounding factor: if women are simply having more sex now because it is less risky to do so, then why have out-of-marriage pregnancies increased over the same period when contraceptives have been improving?

Improvements in birth control technology are a decrease in the “cost” of promiscuity in the
probabilistic sense
. In economic thinking, the cost of premarital sex is determined by the probability that a woman will become pregnant and/or contract a disease multiplied by the costs associated with pregnancy and/or disease. So any factor that decreases either the costs or the risk will decrease the
expected costs
of premarital sex.

For example, imagine that it is 1930 and there is an 85 percent chance that a woman will become pregnant while repeatedly having unprotected sex with a man who is not her husband. Also imagine that if this woman becomes pregnant she loses the opportunity to marry a man with a good income (since she now carries the stigma of having borne an illegitimate child), and that as a result of this lost opportunity, she misses out on $50,000 in future income that she would have gained had she not become pregnant and married a man with a good income instead. Her cost of premarital sex without protection, then, is:

Now instead imagine that latex condoms are available and she is able to convince her partner to use one when they have sex. If the chance of becoming pregnant is 45 percent with a latex condom, which was actually the failure rate of condoms in 1934 (reported by Kopp), then now the expected cost of premarital sex is:

0.45 x $50,000 = $22,500

Giving her the option of sex with a condom has reduced the cost of premarital sex by $20,000.

Any economist will tell you that the quantity demanded of a good or service will increase when the price falls, which is why a standard demand curve is downward sloping when drawn on a graph with quantity on the horizontal axis and price on the vertical axis. So, it isn't that surprising that when contraceptives became more effective at reducing pregnancy and disease, more women (and men, of course) chose to have sex before marriage. And, of course, some of these women will still become pregnant because even with contraceptives the risk of pregnancy has not dropped to zero. In fact, statistically speaking, 45 percent of sexually active women will become pregnant.

Despite improvements in contraceptive technology, the number of pregnancies to women who are not married has not fallen; it has increased dramatically, which suggests that there has to be more to this promiscuity story than individual women making rational choices to have premarital sex based on the efficiency of contraceptive technology.

To understand what has happened, consider a very simple model in which there are two distinct groups of unmarried people who are reluctant to participate in premarital sex in a society in which sex outside of marriage is very much frowned upon. The people in the first group avoid premarital sex because they are worried about unplanned pregnancy but not because of the stigmatization of premarital sex. In the second group, the people avoid premarital sex because they are worried about the stigmatization of premarital sex but not about an unplanned pregnancy. Of course, in reality, everyone will worry a little bit about both pregnancy and stigmatization, but this distinction into groups will make clearer the following explanation as to how attitudes have changed.

Now let's introduce effective birth control to these two groups of previously celibate people. Premarital sex is still stigmatized, but now a small number of people, those who care only about the risk of pregnancy, will decide to become more adventurous. They form a small group of relatively promiscuous people. Over time, others begin to join this group. They do this not because of the reduced risk of pregnancy but because the behavior of the group has changed what society sees as socially acceptable. The
people in the first group join because the pregnancy risk has fallen, and the people in the second group join because the act of premarital sex is now less stigmatized.

So, everyone is having more sex outside of marriage because it has become less risky and more socially acceptable. Where there is always a chance of pregnancy when a man and a woman have sex, an increase in the number of sexual “events” between unmarried couples is bound to increase the number of births outside of marriage. Add to that the fact that birth control effectiveness has decreased births within marriage, then the rise in the
share
of births to unmarried woman is not only unsurprising—it was a mathematical inevitability.

According to Jeremy Greenwood and Nezih Guner, whose research this whole section is based on, the availability of the birth control pill has played only a small role in the increase in premarital sex. They estimate that less than 1 percentage point of the 75 percent of unmarried teenagers having sex in 2002 is the result of the availably of the birth control pill. They argue that we shouldn't take this to mean that contraceptive technologies are unimportant, but rather that the pill is only one of several effective birth control options, all of which have contributed to the social change that has led to an increase in promiscuity.

YOU PROBABLY KNOW THE BENEFITS OF SEX, BUT WHAT ARE THE COSTS?

In Jane's story, we met two distinct groups of women. The women in the first group, those who had little education or hope of a bright economic future, were promiscuous because the costs of promiscuity for them were not high. The women in the second group, those who were both well educated and economically independent, were promiscuous not because the cost was low, in fact the cost was quite high, but because they could afford these costs.

These specific costs that I am talking about don't include the daily wear and tear that raising children alone imposes on a woman; those costs are significant but vary from individual to individual. The costs I am talking about are very specific—they are costs incurred by women and men who fail to complete their education and/or are unable to invest as much in their careers as they might have had they not had a mistimed pregnancy. These costs are important to our story, as they have evolved over the past fifty years as promiscuity has become more common.