Wednesday, October 5, 2011

Spot the Problem: Answer

The economonomadollars have been claimed; congratulations to T-Bone and TAllen, and I look forward to answering their questions. 

Below is my solution:

When you're evaluating the biological effect of a drug on HIV transmission, what matters is not the HIV transmission rate per 100 person-years.  What matters is the transmission rate per sexual encounter.  For someone deciding whether it's a good idea to take this drug, the question is how much it increases or decreases the probability of HIV transmission per encounter.  That is the fundamental biological property of this drug that the study appears to be targeting. [We might also be interested in the effect of drugs on the spread of disease, but they do not appear to be talking about that here].

The problem with letting rate per year stand in for rate per encounter is, it seems likely that people with a more effective contraceptive might just be having more sex.  Because the overall cost of sex is lower when you're using a drug that more effectively prevents pregnancy, right?  Indeed, even if the transmission rate per encounter is identical, they ought to be transmitting more HIV per person-year.

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Anyway, this is a serious flaw in either the study or the reporting.  Either the study doesn't address it, or the writer doesn't. It seems like someone should be hired (not necessarily an economist, though an economist would do) to just sit around and point out obvious flaws in research that really matters a whole lot.  The next obvious question is, why isn't that happening?

If the problem is at the NYT (and yes, the NYT has a serious problem in this area, regardless of whether this particular article is an example of it), then it's not too hard to see why they don't hire someone to fix it. Most of their readers don't notice or care, and you can write more sensational articles for those customers if your standards are lower.

And if the problem is in research in other fields...well, it's easy to see why they might not want someone shooting down all their ideas, either...but now we can at least ask where the funding comes from.  Someone who's interested in solving big medical problems in Africa might want to hire a bunch of medical types to study these issues, together with some other guys to keep them in check.

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