This is all based on unfounded assumptions about who has sex with whom. If you make a graph in which vertices are people and two people have an edge between them if they've had sex, then the structure you actually get is surprising. Here's a real sex graph; bear in mind that this is from a high school, so the things I say in the rest of the post may not apply outside high schools and colleges:<p><a href="http://www.soc.duke.edu/~jmoody77/chains_pressfigure1.jpg" rel="nofollow">http://www.soc.duke.edu/~jmoody77/chains_pressfigure1.jpg</a><p>You've got a lot of two-person monogamous pairings, a smaller number of triads, scattered chains, and then this BIG, HAIRY THING that's vaguely ring-shaped. It doesn't have promiscuous hubs; you can stop the spread of STDs by trying to get as many people as possible to use condoms and get STD screening, thus breaking the chains. It's almost a spanning tree.<p>This structure can be generated from two simple rules:<p>1. People tend to date other people with a similar amount of past sexual experience.<p>2. People avoid dating the exes of other people who are close to them in the relationship graph, since this makes them look bad to their friends, exes, and so on. This accounts for the lack of short cycles.<p>This was theoretically confirmed by some researchers who wrote computer simulations to try to come up with similar-looking relationship graphs, and succeeded brilliantly:<p><a href="http://www.soc.duke.edu/~jmoody77/chains.pdf" rel="nofollow">http://www.soc.duke.edu/~jmoody77/chains.pdf</a>
It seems he chose the simulation parameters without any regard to what the real life numbers are. Anyone who has studied complex systems will tell you this is a big deal. In things like weather simulations, a small change in initial conditions makes for huge differences later on. In something relatively simple like this, it could mean that you are falling on one side of a differential equation or the other.<p>I mean seriously. Half the folks who often have sex will have AIDS?
Better than that would be for our society to get over the stigma around STDs and STD testing. As unromantic as it is, it should be uncontroversial to ask someone for a copy of a recent STD test. Even having cards would be nice, on a purely opt-in basis.<p>People will whine and moan about the privacy concerns, but when it comes right down to it people with untreated or untreatable STIs should not be having sex (and if they are their partners should be made aware.)
The key bit that this author is missing is prostitutes as the "high-activity players". If it's easier for people to get with "low-activity players", it naturally reduces the activity of the "high-activity players".<p>Also, the "high-activity players" modeled as 1 per 10 days seems pretty low, to me. In an extremely conservative society using prostitutes as a sexual outlet for unmarried young men, I would expect rates in excess of 10 per day, not 1 per 10 days.
Of course, none of this changes one ironclad rule:<p>No sex is the safest kind of sex.<p>Not sarcastic and not that I am celibate- but if you personally really wish to avoid STD's, there is a very clear solution.<p>Also, I'm not quite humanitarian enough to raise my personal risk exposure for the sake of lowering society's risk exposure.
Well, there certainly are statistical problems you can't solve without math or simulations, but this isn't one of them. Landsburg is obviously wrong. You only have to think about the extremes (ie. nobody having sex at all, and everyone having sex with everyone) to see that.<p>He also misunderstands the dating pool. It isn't as if promiscous people have a calendar and go to the bar determined to hook up with someone every 100 days, then when they're done think "that was nice, I'll do that again in 3 months." They go to the bar frequently and hook up every time they get the opportunity. Hookups with less promiscous partners don't sate their appetite or reduce at all the number of hookups they'll make later.
There's a story about G H Hardy coming across a geneticist's work and proving that recessive genes persist at an equal concentration, against the original author's claims. This article reminds me a lot of that, where an expert in another field says "let me just check that for myself, errrr!".<p>I believe the Hardy story is told in C P Snow's foreword to A Mathematician's Apology, and the result is now well known: <a href="http://en.wikipedia.org/wiki/Hardy–Weinberg_principle" rel="nofollow">http://en.wikipedia.org/wiki/Hardy–Weinberg_principle</a>
It's nice to see confirmation of this. I got similar results on the simulation I wrote: <a href="http://github.com/philwelch/SexSim" rel="nofollow">http://github.com/philwelch/SexSim</a>
See my comment here: <a href="http://news.ycombinator.com/item?id=1407984" rel="nofollow">http://news.ycombinator.com/item?id=1407984</a><p>I'll check back when I'm less busy to compare how our simulations are set up. Mine was very quick and dirty and naive, based on uniform random distributions no less, so I'm fully open to the possibility we're both wrong.
This code refutes a claim the author didn't make.<p>He was saying that it is in your personal best interest to convince people more sexually conservative than you to start having more sex, which reduces your individual risk. I don't remember him making any claims about the overall benefit (or lack thereof) to the population except for the admittedly misleading title of the book and example.<p>I have no idea whether the claim he did make is true or not, but this particular program doesn't get us any closer to finding out.
The coder has failed to grasp the assumptions, the logic, or the conclusions of the argument he thinks he's addressing. Details here: <a href="http://www.thebigquestions.com/2010/10/04/the-python-misinterpreter/" rel="nofollow">http://www.thebigquestions.com/2010/10/04/the-python-misinte...</a>.
As he showed, it's not a 'paradox'.<p>Actually, it never was, since that's not what paradox means in the first place.<p>But he did show it wasn't true at all.<p>But even if he hadn't, it would -never- have been safer for the 'sexual conservatives'. More sex always means more risk for them, no matter the time frame.