I'm torn here. Do I tell you that's a good point because combination strategies can be much more effective at preventing pregnancy, or do I let you know that the efficacy rate for STIs are subject to the same forces as the efficacy rates for pregnancy?

I guess I can do both. You'll decide what risk to take in any case.

The amount of protection that you can get from a condom against STIs is not as good as the amount of protection you get against pregnancy. Not everyone can give you an STI (about 20% of the population) whereas most straight couplings can lead to pregnancy (about 90% of people of childbearing age are fertile). So that increases your odds of a good outcome. Some people are honest about their STI status, and that also increases your odds of a good outcome - but don't forget that some people do not even know that they have an STI, and others may be in denial or crazy or sociopathic - and if you're having casual sex, you really can't be sure about a person's moral character and sanity level.

Your chance of getting an STI while using a condom would be a lot higher than 50% if you had a partner with a disease for the rest of your life. If you have random partners, and 1/20 people has an STI and some of them don't know it, and some of them aren't honest... I'm not sure what your chances are, but if you're successful with finding partners, it could be substantially worse than a 2% lifetime risk.

You may want to try looking up rates of STI among people who have non-relationship sex.

Another possibility is to find a special friend and get tested together.

If that won't work, a combination strategy (like condoms with spermicide) could be a significant improvement. You may want to research nonoxynol-9 before using it. I've heard that it increases the chance of disease transmission.

Pretty much all the non monogamous people I know get regular tests. So yes, most people use testing in addition to condoms. I don't have casual sex any more, really, but I never caught an STI when I did.

Oh, and most condoms sold in the UK contain spermicide.

Public Service Announcement Collection

by Eliezer Yudkowsky 1 min read27th Jun 2013330 comments

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P/S/A:  There are single sentences which can create life-changing amounts of difference.

  • P/S/A:  If you're not sure whether or not you've ever had an orgasm, it means you haven't had one, a condition known as primary anorgasmia which is 90% treatable by cognitive-behavioral therapy.
  • P/S/A:  The people telling you to expect above-trend inflation when the Federal Reserve started printing money a few years back, disagreed with the market forecasts, disagreed with standard economics, turned out to be actually wrong in reality, and were wrong for reasonably fundamental reasons so don't buy gold when they tell you to.
  • P/S/A:  There are many many more submissive/masochistic men in the world than there are dominant/sadistic women, so if you are a woman who feels a strong temptation to command men and inflict pain on them, and you want a large harem of men serving your every need, it will suffice to state this fact anywhere on the Internet and you will have fifty applications by the next morning.
  • P/S/A:  Most of the personal-finance-advice industry is parasitic and/or self-deluded, and it's generally agreed on by economic theory and experimental measurement that an index fund will deliver the best returns you can get without huge amounts of effort.
  • P/S/A:  If you are smart and underemployed, you can very quickly check to see if you are a natural computer programmer by pulling up a page of Python source code and seeing whether it looks like it makes natural sense, and if this is the case you can teach yourself to program very quickly and get a much higher-paying job even without formal credentials.