Monday, October 6, 2014

Does free contraception reduce pregnancy?

A natural experiment suggests that the answer is "yes"


An experiment conducted in St Louis provided 1404 girls aged between 14 and 19 with free contraceptive advice and free long-acting contraceptive devices ... The comparison group was that of similar girls in the rest of the United States who were not included in the experiment. 
The researchers found that, by giving both free advice and free contraceptives, the rates of pregnancy, live birth and induced abortion declined precipitously by comparison with national averages. ... On the face of it, the experiment was a triumphant success.

Until you look a little closer at how the experimental group was "selected":

The young girls were drawn from those who resided in St Louis or sought contraceptive services in selected community clinics, and furthermore had no desire for pregnancy for at least 12 months. These girls, then, were a self-selected group...

BOTTOM LINE:  the observed different between the groups is the sum of the "treatment" effect (the effect of the contraception) and the "selection" effect (that girls less likely to get pregnant were in the experimental group).  This is why randomized experiments are so much easier to interpret.   

5 comments:

  1. Giving teenage girls free birth control -- especially long-acting implanted devices -- could slash pregnancy and abortion rates to well below the current U.S. average, new findings suggest. In a study of 1,400 teenage girls, researchers found that counseling and free contraceptives substantially cut the girls' rates of unplanned pregnancy and abortion. Over three years, their annual pregnancy rate averaged 34 per 1,000 girls -- versus a rate of 158 per 1,000 among all sexually active teenage girls in the United States.

    Meanwhile, the abortion rate was 9.7 per 1,000 girls in the study, compared to a national abortion rate of 41.5 per 1,000 sexually active girls, the researchers report in the Oct. 2 issue of the New England Journal of Medicine. IUDs and implants are substantially more effective than the Pill or condoms, which are currently the top birth control choices among U.S. teens, according to the American Academy of Pediatrics (AAP).

    The "magic" of IUDs and implants, according to Bill Albert (chief program Officer for the Washington, D.C.-based campaign to prevent Teen & unplanned pregnancy), is that they are put in place and then last for years -- or until a woman decides to remove them. "These types of birth control are 'set it and forget it,'" Albert said. "They don't rely on perfect use."

    "This study shows that the IUD and implant help reduce teen pregnancy," said Dr. Vanessa Cullins, vice president of external medical affairs for Planned Parenthood Federation of America. " IUDs and implants are safe for most women, including adolescents and women who have not yet children, and they are an especially good option for young women who want to delay starting their families for a few years, so they can be the best parents they can be." As for cost, under the Affordable Care Act, many insurers have begun covering prescription birth control methods without copays.

    When parents discuss these issues, their kids tend to delay sex. And when they do have sex, they're more likely to use contraception.

    Work Cited:
    Norton, A. (2014) Free, Long-Acting Contraceptives May Greatly Reduce Teen Pregnancy Rate. Retrieved from: http://consumer.healthday.com/women-s-health-information-34/abortion-news-2/giving-free-contraceptives-to-teens-brings-steep-drop-in-pregnancies-study-692295.html

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  2. This experiment could’ve easily represented a moral hazard. There is a concern that when people of health insurance, they will be more likely to visit the doctor every time they have a little cold. Many politicians and religious leaders actually argue that giving women access to education and contraceptive devices will cause them to exhibit this type of behavior by engaging in sexual behavior that will leave them susceptible to pregnancy. This experiment you wrote about, despite its design flaws, contradicts the idea that most women who have access to education and birth control will engage in this type of risky behavior.

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  3. It appears to be clear the offering of free contraception to teen girls does reduce pregnancy. Is it obvious that the outcome of any experiment or project like this will have positive outcomes? Let’s ask – If we give one group of 18 year old boys a free sports car and another group a free bus pass will there be one group with more accidental deaths? It would be easy to divide the groups, those with the cars and those relying on public transportation. Perhaps we can look at something less controversial, like free access to health care. Is a person with insurance (free or not) more likely to go to a doctor with every little symptom? Perhaps at first, but over time visits to the doctors tend to reduced. However the chance of discovering a problem early on is increased, even something as simple as high BP. Back to the girls in the study, a question is because of free contraception will more people engage in sexual activities, increasing the likelihood of negative consequences other than undesired pregnancy? Because there is a perception that there is no risk in having sex (can’t become pregnant), it may increase the frequency or number of partners someone is with, increasing risks of other undesired outcomes. To find the probability of the increase in sexual activity may be difficult, also develop the two groups to conduct the experiment may be the first challenge.

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  4. It’s official. One truly never knows the limits to which theories of economics can be applied! In this case, the author makes the point that randomized experiments, in which variables are assigned to specific characteristics of that experiment, make it easier to interpret experiment results over an experiment where the variables are not random, but rather pre-determined. In this case, the test group was for all intents and purposes “self-selected,” since they did not want to get pregnant and had previously sought out contraceptive services or advice. Allowing this pre-determined variable into the experiment, we add a layer of subjectivity that removes the randomness (and, to a degree, the validity) of the experiment.
    Had the folks running the experiment assigned truly random variables for each possible quantity (girls becoming pregnant), they would have been able to more objectively quantify the risk or uncertainty of becoming pregnant.
    Ultimately, these experiments are not for the sole use of economists. They can be used in any variety of situations where a control group is left untreated and the experiment group is given a variety of stimuli. According to Wikipedia, these experiments are not only used for a number applications, they also date back to the times of the Old Testament!

    References:
    Froeb, McCann, Ward, Shor: (2014) Managerial Economics. A Problem Solving Approach, Ohio: South Western Cengage Learning
    http://en.wikipedia.org/wiki/Randomized_experiment

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  5. This definitely is a case where the experiment can not be considered valid because the control group does not match the experimental group. Teenage girls who actively seek contraception are, of course, going to be less likely to become pregnant than girls who may or may not seek contraception. However, I can also see a case for a moral hazard here. While it may not be evident by the bias in this experiment, if a more scientific study should be conducted, the researchers should explore the moral hazard possibility that girls who are using contraception are more likely to be sexually active than girls who are not using contraceptive. The outcome of that study, and if the moral hazard is proven true or false, could lead to some very interesting dialogues surrounding this issue.

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