International comparisons

From RNZ

New Zealand has rates of sexual violence against teenagers above the global average, ahead of even a badly afflicted Australia, according to new research.

and from the Herald

New Zealand has rates of sexual violence against teenagers above the global average, more than even badly afflicted Australia, according to new research.

The research paper is here, and I would guess there’s a press release out there somewhere. The Science Media Centre commentary is here.

The first thing to note is that the new research tells us absolutely nothing new about rates of sexual violence against teenagers in either New Zealand or Australia.  Like many studies producing global estimates, the research takes the numbers already available for various countries around the world and tries to combine them.  For countries without reliable data this can give us new information, but not for countries that already have reasonable-quality data.  So, the research tells us what we already know about the problem in New Zealand — it is bad.

The second thing to note is that while the number for New Zealand is higher than the number for Australia, the difference is much less than the study’s uncertainty estimate (‘margin of error’). The real conclusion is that NZ is about as bad as Australia on this front.  In fact, if you look at the figure for women currently aged 20-24 it’s actually lower in NZ (24.5%) than in Australia (25.4%).  The fact that Australia is just as bad shouldn’t reduce our concern about sexual violence in New Zealand; international comparisons don’t help for telling us whether we have a problem.

Doing a global study like this is useful to the extent that you can get estimates for countries without good data. The researchers tried to correct for various biases, such as narrow definitions of sexual violence in some of the component studies, different age limits, not including boys as victims, and whether the questions were asked face-to-face or not.  They didn’t have any data in some places, and so patched in estimates from nearby countries.  It’s not clear that this all worked.

If you look at the estimates from across the world there are some surprising numbers.  Wars are generally recognised as bad for all sorts of violence, but the number for New Zealand women currently aged 20-24 (25.4%) is substantially higher than the Democratic Republic of the Congo (17.6%) and South Sudan (20.9%) which have recently suffered actual civil wars, and Yemen (12.7%), which is currently in one.  It’s notable that this low estimate is identical for Yemen and Syria, Sudan, Saudi Arabia, Afghanistan, Qatar, Palestine, Libya, Iran, and Iraq — it’s an example of using data from one country when you don’t have data for another. These surprising results come with very wide uncertainty intervals: Yemen’s is 3.8% to 30.7%, and since most such intervals underestimate the true uncertainty the estimate basically amounts to  ¯\_(ツ)_/¯

There just isn’t much information about rates of sexual violence in many countries, so even if you cared about international comparisons, estimates for every country aren’t all that useful.  I’m a bit surprised the Lancet thought this one was informative enough to be worth publishing.  The best you can really say about the research paper is that it gives an opportunity to get headlines about this problem, and maybe potentially do something to reduce it.