maradydd: (Default)
maradydd ([personal profile] maradydd) wrote2008-11-03 04:01 pm

Because I hate bad statistics

The following is a response to this post about California's Proposition 8. I left it as a comment there, but comments are moderated, and somehow I don't think it will get posted. Thus, y'all get to read it here.

Amy writes:
"After legalizing same-sex marriage 5 short years ago HIV/AIDS has increased in Massachusetts with more than 40,000 being infected each year."
I don't know what Amy's source on this figure is, but I did some research, and this claim is not only wrong, it's wrong on several orders. The first same-sex marriage in Massachusetts was performed on May 17, 2004. Since then, the prevalence of HIV/AIDS -- "prevalence" meaning "how many people have it" -- has increased, but the rate of increase has fallen off sharply.

First of all, according to the Massachusetts Office of Health and Human Services' epidemiology department, whose 2007 report you can read for free, as of November 1, 2007 there were only 16,866 people known to be living with HIV/AIDS in Massachusetts.

How could there be 40,000 new cases a year if the total number of cases in the state is less than half that?

The report also examines the trends in HIV infection. As you can see in the chart (the right-hand one on the first page), the number of newly diagnosed HIV infections dropped sharply between 2004 and 2005 and again in 2006. If you look at the first page of the data tables, you'll see that in 2003 the total number of cases was 14,992 and in 2004 it was 15,633. That's an increase of 641 cases. In 2005 the number was 16,217 -- an increase of 584 cases. In 2006 the number was 16,621 -- an increase of 404 cases. For the first ten months of 2007 it was 16,866 -- an increase of 245 cases.

What we can see from this is that the rate of new infections in Massachusetts has not only fallen since the introduction of gay marriage, it has fallen more quickly. 57 fewer people got infected in 2004 than in 2003. 180 fewer people got infected in 2005 than in 2004. And 159 fewer people got infected in the first ten months of 2007 than in all of 2005. If we project that trend out to the end of 2007, that would be 190 fewer new infections.

I'm sorry, Amy, but your argument doesn't hold up.

Forgot one

[identity profile] dv-girl.livejournal.com 2008-11-04 12:41 am (UTC)(link)
It's a shame that it didn't list the sexuality of the newly infected. New cases of HIV infection has been on a serious decline in the gay community for close to a decade now. It's mostly kids with lacking sex education that are getting hit these days.

Re: Forgot one

[identity profile] maradydd.livejournal.com 2008-11-04 12:55 am (UTC)(link)
The data tables sort of go into that, on page 15 where it talks about exposure mode. However, the data aren't broken down by year; it merely looks at all diagnoses from 2004-2006.

Interestingly, male/male sex without IV drug use and "undetermined" are the two lead causes, at 37% -- in fact, undetermined is highest. (Though, note that "heterosexual sex with partners with unknown risk and HIV status" is rather disingenously included under "undetermined". If that were combined with the "heterosexual sex" category, that would be a whopping 33% of cases. Dammit, people, use condoms!)

I can understand why they didn't put that in the report, though; getting people to tell the truth about their sexual orientation is hard due to stigmatisation (boo, hiss), and people are probably self-reporting about how they got infected.