One frequently hears the claim that "Abstinence is the only 100-percent-certain way to avoid pregnancy and sexually transmitted diseases (STDs)." Proponents of abstinence-only sex education say it, the Bush administration says it, and even advocates of other forms of birth control say it. In many ratings of the effectiveness of birth-control methods, abstinence is listed as being as effective as hysterectomy and more effective than vasectomy: 100 percent. What is remarkable about all this is that this statement is not true in almost any sense. As I will show, the only sense in which it is true is one that provides no particular motivation for someone to choose abstinence over other forms of contraception and disease prevention. Understood in any way other than this trivial one, it is either extremely misleading or false.

First, the sentence is not strictly true: even perfect abstinence does not provide one with 100 percent certainty of avoiding STDs, because most are transmittable in other fashions (e.g., accidental needle sticks, etc.). It is also possible to become pregnant while abstinent under some definitions of the term, because semen can occasionally contact the vagina even without vaginal penetration. But perhaps this misses the desired point: one can be certain of not getting pregnant or getting an STD through sexual contact as long as one defines abstinence as avoiding any action that allows any exchange of bodily fluids, including contact between semen and female genitalia. Then, one can maintain that abstinence provides 100-percent certainty of avoiding pregnancy or sexual transmission of STDs.

The claim is true in this fashion: if one does not perform a given action, then there can be no consequences of performing that action. So we can hold the above claim to mean, "For each case where one could perform a sexual act, not performing one will avoid the consequences of performing sexual acts," which is, of course, true.

But that is not the way that the claim is used. Abstinence is put forth not as a single action, but rather as a method of birth control. To judge the effectiveness of abstinence in this respect, we need to judge not only whether the individual act of abstaining from sexual intercourse provides the stated 100-percent benefits, but also whether choosing to use abstinence as a method of birth control provides such results. The difference between the two is significant, as it points to the fundamental difference between the way abstinence and all other birth-control methods are treated when determining their success rates.

In the context of assessing the effectiveness of a birth-control method, one must differentiate between a method's theoretical effectiveness and its "use-effectiveness" or "typical use-effectiveness." The theoretical effectiveness of a method of birth control is a "perfect world" calculation-no one ever forgets to take a pill, condoms never slip and are always put on before any genital contact, etc. It is therefore of little interest to the average person except as an intellectual exercise. What we want to know, when choosing a method of birth control, is how well it will work in the real world to prevent pregnancy. It is here that abstinence is treated radically differently than any other method of birth control.

The first reason for this is practical and yet still points to the problem in making this comparison. The use-effectiveness of a given form of contraception depends, of course, at least in part, on the rate of sexual intercourse, though this is not always made clear. The chances of becoming pregnant while utilizing a given method of birth control are greater the more frequently one has sexual intercourse. One source notes that "Researchers presume that married women have coitus three times weekly and their statistics assume [this] 'married model.'"¹ Thus, unless one averages thrice-weekly intercourse, the actual use-effectiveness of one's birth control will differ from that calculated on the "married model." If one has sex more frequently, the success rate will be lower; if less frequently, the success rate will be higher.

Whether this model is accurate for most marriages, or whether it is used for other lists, it is clearly not used for any abstinence model. For in determining the effectiveness of abstinence, but only of abstinence, no sexual intercourse is presumed. Immediately the comparison is suspect, if only for the reason that we are comparing apples and oranges-the success rate of the pill assumes sex thrice a week, while the success rate of abstinence presumes none. Naturally, both the theoretical and use-effectiveness of various other methods of birth control, including none whatsoever, increase dramatically when one assumes no sexual intercourse.

Since the definition of abstinence is "no sexual intercourse," it is perhaps unfair to criticize someone reporting the success rate of abstinence on grounds that they have not presumed regular sexual intercourse. But this points to the real problem, which is that the "100-percent-success rate" is only theoretical. If we assume one always succeeds in avoiding sex, then we can fairly assume the success rate of abstinence to be 100 percent (with the exceptions noted above).² But the use-effectiveness-the success rate in the real world-of persons trying to use abstinence as their method of birth control is far less than 100 percent because they do not always succeed in avoiding sexual intercourse.

This is not news, I suspect. People trying to be abstinent can and do fail, and sometimes pregnancy results. What is astonishing is how little attention is paid to this fact. On list after list of effectiveness of birth-control methods, abstinence is ranked at the top, or given special mention because of its 100-percent-success rate. This pride of place is confusing and quite possibly dangerous. Because of the difference in what is being measured, to trumpet the value of abstinence relative to other methods is at best deceptive, at worst irrational. Since nothing of what I have said above is new or surprising, and since the use-effectiveness of abstinence is surely significantly less than its theoretical effectiveness, how does abstinence continue to be labeled as the most effective method of birth control on the grounds of its theoretical effectiveness, even when the use-effectiveness of other methods is reported?

One reason may be that the use-effectiveness rate of abstinence, or exactly how we should calculate it, is unclear. Many sources give no answer at all; and though some recent research has attempted to properly determine abstinence's use-effectiveness, its results have not made their way into the popular understanding.³ While we know a great deal about use-effectiveness rates for other methods of contraception, a recent review of the literature on sex education argued, "We still know very little about abstinence and how often adolescents [or, presumably, any other persons] fail to use abstinence consistently."⁴ Given this, how can anyone label abstinence as 100-percent effective, even in theory, without a very serious caveat to the effect that we have no clear idea how effective it is in practice?

I suggest that the reason is a "Heads I win, tails don't count" way of thinking. When a couple attempts to avoid having sex as a means of birth control and succeeds, they have properly used abstinence as their method of birth control, and lo and behold, they achieve 100-percent success at preventing pregnancy. If, on the other hand, they attempt to use abstinence as their method of birth control but end up having sexual intercourse, they have not abstained and thus haven't used abstinence. They are then included in the group of people who used no method of birth control. The success rate of abstinence remains 100 percent.

This kind of language game sustains the tenet that "abstinence is the only sure way," but it is intellectually dishonest. The sentence "Abstinence is the only 100-percent-certain way to avoid pregnancy and STDs" is true only in a trivial way that also applies to all other forms of birth control-assuming no sexual activity, there will be no impact from sexual activity, regardless of one's chosen method of protection. And when one tries to find out the number of women who become pregnant while trying to use abstinence as birth control, one encounters at best the misleading language about failing to be abstinent-and therefore not using abstinence. Whether one takes them regularly or not, if one is depending upon a birth-control pill to prevent pregnancy, one is using the pill as one's method of birth control-this is the difference between theoretical and use-effectiveness. The same difference applies to abstinence as a birth-control method, and it's time we discover and properly report those numbers as well. If we are going to talk about slipping condoms, failures to take pills on time, etc. as relevant to how effective these methods of birth control are-and we should-then we had better talk as well about failures of will in avoiding one of the most fundamental drives that humans have.

Notes

1. http://www.womenshealthspecialists.org/health/bcontrol/effect/effectiveness.shtml, February 24, 2003.

2. Actually, the success rate is not 100 percent, but rather undefined. The success rate can be read as a ratio of "times one did not get pregnant from sexual intercourse" over "times one had sexual intercourse." If the denominator is zero, the ratio is undefined, even if the numerator is zero as well. Hanno Bulhof pointed this out to me.

3. Steven D. Pinkerton, "A Relative Risk-Based, Disease-Specific Definition of Sexual Abstinence Failure Rates." Health Education and Behavior 28, no. 1 (February 2001).

4. Clara S. Haignere, Rachel Gold, and Heather J. McDaniel, "Adolescent Abstinence and Condom Use: Are We Sure We Are Really Teaching What Is Safe?" Health Education and Behavior 26, no. 1 (February 1999): 43-54.

Stephen Hanson is in the Department of Social Sciences at McNeese State University in Louisiana.