Interesting probability question.

[facekicka]

Who is more likely to get pregnant? A woman who is completely abstinent and takes no form of chemical birth control, or a woman who takes chemical birth control and has sex with whoever she pleases. I think that it's very likely that in at least some circumstances (depending on the age,location[ie, in the inner city or on a college campus], social habits) the abstinent women is more likely to get pregnant as a result of rape than the sexually active women would in any matter. I think this idea could have some implications in the abortion argument, especially for those who are against abortion except in the case of rape/incest.

[KathleenStand]

Are you serious?

[madnak]

Chemical birth control is generally not that reliable. Rape is more common than some of us would like to believe, but it is still relatively rare.

Of course if the birth control woman had sex once per month and always used a condom, while the abstinent woman had a habit of strolling through Central Park after midnight, it might be possible. But it's a bit of a stretch.

I am all for promiscuous sex, but I think this line isn't going to work.

[MrMon]

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Chemical birth control is generally not that reliable.

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Huh? Properly taken, birth control pills are as high as 99.7% effective. How reliable do you need?

[HLMencken]

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Chemical birth control is generally not that reliable.

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Huh? Properly taken, birth control pills are as high as 99.7% effective. How reliable do you need?

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How often should we estimate for a consenting sexual encounter? Let's say 1 per week.

I think a woman is less than 0.3% likely to be raped on a given week (or 3 of every 1000 would be raped every week, so for a town of 30,000 that would be 90 rapes per week). So given the OP's scenario, you'll need a LOT higher than 99.7% reliability of birth control for his assertion to be valid.

[madnak]

Hmm. Looking for statistics it seems that sexual assault may result in pregnancy more often than I had thought.

HLMencken, the chance of being raped is based on many variables and so the rapes can't be assumed to be evenly distributed. A major variable is gender - since we are only taking women into account, there only have to be 45 rapes per week in a town of 30,000. The assumptions in the OP assume a high-risk lifestyle as well, so maybe 20 rapes would be needed.

Still quite a lot of raping. But if the birth control user also uses condoms, then only 0.2 or fewer rapes would need to occur. So if she uses birth control as well as condoms and has sex once per week, I think it's reasonable to assume that she is at a lower risk of pregnancy than the abstinent woman with the risky lifestyle.

[PoBoy321]

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Chemical birth control is generally not that reliable.

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Huh? Properly taken, birth control pills are as high as 99.7% effective. How reliable do you need?

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If I understand t correctly, when properly taken, birth control pills are like 99.999% effective. The reason that their numbers are lower has to do with improper administration (but I could be wrong).

[dragon14]

Here's a link to Detroit crime stats. Detroit is known as one of the most violent cities in the U.S. Link (http://www.areaconnect.com/crime/compare.htm?c1=Chicago&s1=IL&c2=Detroit&s2=MI)

Per my calculations Detroit would have 719 total instances of rape a year. In cities with high violent crime rates women tend to outnumber men by 8-10%. So I'll go with women as 54% of the population or 477,880 in Detroit.

The odds of being raped are thus 1 in 664. Then we have to check the odds of becoming pregnant from unprotected intercourse. I got a rate of 1 in 40 for the odds of a woman becoming pregnant from unprotected intercourse.

Thus the odds of becoming pregnant from rape appear to be 1 in 26,560 over a years time. Someone else can look up the birth control data but birth control. This isn't a perfect analysis (for instance not all rapes in Detroit are of Detroit residents, etc.).

[HLMencken]

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Thus the odds of becoming pregnant from rape appear to be 1 in 26,560 over a years time. Someone else can look up the birth control data...

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So the probability of not getting pregnant by rape in a year in Detroit is approximately 99.9962% by your analysis. In order for a woman to have sex 40 times in that year on birth control and have a higher probability of not getting pregnant, the reliability of birth control for a single encounter would have to be 99.99991%. Without looking up the numbers, I can guess that that's a bit higher than practical.

[bholdr]

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Per my calculations Detroit would have 719 total instances of rape a year.

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nice post, d14, BUT, those stats are based on the number of REPORTED rapes. rape may be the most under-reported (violent felony)crime out there...
study (http://72.14.207.104/search?q=cache:Lg3dtGcBFvoJ:www.vawnet.org/SexualViolence/PublicPolicy/MakingSenseofRape.pdf+rape+reported+vs+unreported+ &hl=en&gl=us&ct=clnk&cd=2):

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. In one major national study, victims reported rapes to police in only 16% of cases (Kilpatrick, Edmunds, & Seymour, 1992).

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sadly, i think even the 16% is too high an estimate.

that said, the contraceptive user is still much more likely to get pregnant, imo.