When do we care about international comparisons?

I’ve done a bunch of posts recently about international comparisons. A good way to get a headline is to say NZ is the worst (second-worst, third-worst) in the world.  These tend not to be true — what’s usually true is that NZ is the worst among a smaller group of countries with high-quality official statistics.

But when do we even care? I’ll look at three recent examples

• NZ is the worst (only not) in bowel cancer rates, so we need subsidised screening
• NZ is the third worst (only probably not) in child road deaths, so we need to require child car seats up to age 11.
• NZ is the second worst (only not) in imprisonment rates, so we need to change the justice system

When deciding whether to subsidise bowel cancer tests there are just two things that matter: whether it works, and how much it costs. If the screening isn’t effective, we shouldn’t do it. If it is effective, but costs a lot more than other ways of preventing the same amount suffering and loss of life, we should do those instead. It doesn’t matter whether the rates are higher in Austria or Australia. No-one should be taking that into account.

When deciding whether to require child car seats, there are three things that matter: do they prevent injuries, how much do they cost to buy, and how much does the law cost in enforcement and in the (subjective but real) costs of forcing people to do things. If the seats don’t prevent injuries, we shouldn’t use them. If they don’t prevent more injuries than other things we could do at a similar price, we should consider those things first. And to make them compulsory, the benefit has to be large enough to be worth the monetary and non-monetary costs of enforcement, but not large enough that parents will do it voluntarily. If we can satisfy these criteria, we should pass the law, regardless of what is happening in other countries. If we can’t satisfy these criteria, we shouldn’t.

Imprisonment rates are a bit different. It’s not obvious what the ‘right’ imprisonment rate is, so international comparisons are actually helpful in deciding whether the NZ rate is high or low. Comparisons to the whole world are still pointless, but it makes sense to compare to other countries with basically similar legal systems and a fairly high level of trust in government.

Even when we shouldn’t care about what is being done in other countries, it’s often useful to know why they do what they do. That’s why I link to things like the US Preventive Services Taskforce recommendations. It’s not that New Zealand should necessarily do what the US does, but the PTF has more resources for making decision, and they show their working. We can look at their collected evidence and read their rationales, and that’s helpful in deciding what to do in New Zealand.