Posts filed under Politics (194)

Generally good use of survey data in a story from Stuff about the embattled Education Minister.  They even quote a competing poll, which agrees very well with their overall statistic.

The omission, though, relates to the headline figure: “71pc want Parata gone – survey”.  That’s a proportion “among voters from Canterbury”.   Assuming that they don’t mean “voters” in any electorally-relevant sense, just respondents, we would expect about 120 of the 1000 respondents to be from Canterbury. The maximum margin of error is a little under 10%.

The fact that one region has 71% wanting Ms Parata gone when the overall national average is 60% would actually not be all that notable on its own. Since we already expect her to be less popular in ChCh, the difference is worth writing about, but if it’s worth a headline, it’s worth a margin of error.

David Farrar (among others) has written about a recent Coroner’s recommendation that high-visibility clothing should be compulsory for cyclists.  As he notes, ” if you are cycling at night you are a special sort of moron if you do not wear hi-vis gear”, but he rightly points out that isn’t the whole issue.

It’s easy to analyse a proposed law as if the only changes that result are those the law intends: everyone will cycle the same way, but they will all be wearing lurid chartreuse studded with flashing lights and will live happily ever after.  But safety laws, like other public-health interventions, need to be assessed on what will actually happen.

Bicycle helmet laws are a standard example.  There is overwhelming evidence that wearing a bicycle helmet reduces the risk of brain injury, but there’s also pretty good evidence that requiring bicycle helmets reduces cycling. Reducing the number of cyclists is bad from an individual-health point of view and also makes cycling less safe for those who remain. It’s not obvious how to optimise this tradeoff, but my guess based on no evidence is that pro-helmet propaganda might be better than helmet laws.

Another example was a proposal by some US airlines to require small children to have their own seat rather than flying in a parent’s lap. It’s clear that having their own seat is safer, but also much more expensive.  If any noticeable fraction of these families ended up driving rather than flying because of the extra cost, the extra deaths on the road would far outweigh those saved in the air.

It’s hard to predict the exact side-effects of a law, but that doesn’t mean they can be ignored any more than the exact side-effects of new medications can be ignored. The problem is that no-one will admit they don’t know the effects of a proposed law.  It took us decades to persuade physicians that they don’t magically know the effects of new treatments; let’s hope it doesn’t take much longer in the policy world.

[PS: yes, I do wear a helmet when cycling, except in the Netherlands, where bikes rule]

Usually when someone confuses the probability of A given B and the probability of B given A they don’t really understand that these are different, and you have to point it out and explain it carefully. Richard David Prosser manages to be self-refuting,

And he added: “If you are a young male, aged between say about 19 and about 35, and you’re a Muslim, or you look like a Muslim, or you come from a Muslim country, then you are not welcome to travel on any of the West’s airlines…”

He accepted that most Muslims are not terrorists, but said it’s “equally undeniable” that “most terrorists are Muslims”.

actually pointing out himself that p(terrorist|Muslim) and p(Muslim|terrorist) are not remotely similar.  In the same way, although most members of the Pakistan cricket team are Muslims, most Muslims are not members of the Pakistan cricket team.

That doesn’t handle the further pointless complication of ‘people who look like Muslims’, who, as far as I have been able to tell, are not over-represented among terrorists, but this site might be helpful for calibration.

So. 3News reports that the changes to the warrant of fitness rules are going to lead to 2000 jobs being destroyed.  Since this number comes from opponents of the change, it’s almost certainly exaggerated, but how does it compare to the  general rate of job creation and destruction?

According to Stats NZ, in 2009 there were 252 360 jobs lost. Fortunately, there were 223 860 jobs created, even in the depths of the recession.  In 2008, there were 259 920 jobs created and 205 170 jobs destroyed.  So, the WoF change amounts to about 3 days worth of normal background job destruction.  As this shows, jobs always turn over quite rapidly. If we (or, rather, those of you who have cars) stop spending money on WoFs, the money saved will mostly get spent on something else, and will create broadly the same number of jobs there.

Specific job creation or destruction matters a lot in towns that depend on a single employer or industry, but otherwise the headline numbers are rarely as bad as they sound, unless you have one of the jobs.

Stuff has a story from the Sydney Morning Herald on clinical trials in India.  The basic claims are damning if true:

…clinical drug trials are at the centre of a growing controversy in India, as evidence emerges before courts and, in government inquiries, of patients being put onto drug trials without their knowledge or consent…

With a very few exceptions (eg some trials of emergency resuscitation techniques and some minimal-risk cluster-randomised trials of treatment delivery)  it is absolutely fundamental that trial participants give informed consent. Trial protocols are supposed to be reviewed in advance to make sure that participants aren’t asked to consent to unreasonably things, but consent is still primary.  This isn’t just a technical detail, since researchers who were unclear on the importance of consent have often been bad at other aspects of research or patient care.

The Fairfax story mixes in the claimed lack of consent with other claims that are either less serious or not explained clearly. For example

Figures from the drugs controller- general show that in 2011 there were deaths during clinical trials conducted by, or on behalf of, Novartis, Quintiles, Pfizer, Bayer, Bristol Mayer Squibb, and MSD Pharmaceutical.

Of course there were deaths in clinical trials. If you are comparing two treatments for a serious illness, the trial participants will be seriously ill.  When you need to know if a new treatment reduces the risk of death, the only way to tell is to do a study large enough that some people are expected to die.  Even if improved survival isn’t directly what you’re measuring, a large trial will include people who die. In the main Women’s Health Initiative hormone replacement trial, for example, 449 women had died by the time the trial was stopped.  The question isn’t whether there were deaths, it’s whether there were deaths that wouldn’t have occurred if the trials had been done right.

There’s also a claim that families of participants who died were not given adequate compensation as part of the trial.  If there had been consent, this wouldn’t necessarily matter. Lots of trials in developed countries don’t specifically compensate participants or relatives, and there’s actually some suspicion of those that do, because it provides another incentive to participate even if you don’t really want to.

Other sources: Times of India, Chemistry World, a couple of review articles, the Nuremberg Code

Today’s fascinating survey time series: for fifty-five years Gallup has been asking people in the US if they approve of interracial marriage. (via Paul Krugman, in the NY Times)

On the one hand: Yay, progress! On the other hand, one in seven people still not only don’t approve but are prepared to admit this to a random caller on the phone.

The Herald has a story about a new treatment for a very rare blood disorder, and the fact that Pharmac isn’t funding it.

The drug, eculizumab (brand name Soliris), is currently the world’s most expensive, at about NZ$500 000 per year. It’s also very effective.  There’s starting to be a lot of this: we now have the technology to develop specific treatments for a wider range of rare diseases, and most of the rest of that ‘most expensive’ list are replacement enzymes for rare deficiency disorders.   Another recent example is ivacaftor (brand name Kalydeco), which, in about 5% of cases of cystic fibrosis allows the defective chloride transporter protein to work normally.  The result appears to be complete control of the disease, but at a cost of US$300 000 per year. Similar drugs for other variants of cystic fibrosis are being tested.

Funding any one of these drugs would be a minor total cost for Pharmac, because each rare disease is rare. There are only about eight people in New Zealand who would take eculizumab, which would cost only 0.5% of Pharmac’s budget; there would be about 25 who could take ivacaftor, adding up to a percent or two of the budget. The difficulty is that rare diseases collectively are not rare — the European Organization for Rare Diseases estimates that 6-8% of the European Union population have a rare disease and applying that figure to the NZ population still gives 270 000 people.  At $500 000 per person, Pharmac’s total budget would pay for 1500 people to get this sort of very expensive treatment.  At the moment there probably aren’t 1500 people in NZ whose rare diseases are expensively treatable, but there are a lot more than eight.

The patient support group for people with this rare blood disorder obviously think the treatment should be funded

The group’s founder, Auckland artist Daniel Webby, 32 – who almost died from PNH complications – said the funding process did not recognise the rights of rare-disease sufferers.

“They need to recognise that for rare diseases, [drug] development costs are higher per patient. They need to put that into their budget and make sure people get … life-saving treatments when they are available.”

I’m sure Pharmac does recognise this, but changing the national approach to subsidy of health care to give priority to ‘miracle’ treatments for rare diseases is not the sort of decision Pharmac should be making on its own, and the money shouldn’t be taken out of the current Pharmac budget (which is already on the low side).   Kiwis need to decide whether a miracle drug fund is something we want to support and are willing to pay for.

[Update: The Herald has an editorial weighing in strongly against expensive drugs even if effective.  I basically agree, but it’s a pity they don’t have the same attitude to miracle treatments that don’t work]

You may have heard some under-rehearsed radio wittering from me on this topic, so I thought I should write something more coherent.

Last August, researchers from the Dunedin Cohort Study published a paper showing that people who had been heavy cannabis users as teenagers performed worse on cognitive function tests later in life, where this wasn’t true of people who started using cannabis as adults. One natural interpretation of these associations is that cannabis has toxic effects during brain development.  As I pointed out at the time, the evidence isn’t overwhelming (since it’s a relatively small study and we know environmental factors can lead to differences as big as those observed) but was somewhat persuasive and is probably better than other studies on this topic.

Now, a Norwegian economist has argued that the results could be explained by purely sociological factors: that people from low-socioeconomic status backgrounds are more likely to use cannabis, and to perform worse on cognitive function tests, and that the difference in cognitive function tests tends to increase over time after school.  He is correct; this could explain the published results.  However, the Dunedin Cohort Study researchers have done further analyses in response, and while the socioeconomic explanation was reasonable, it seems to not be true.  Both the relationship between socioeconomic status and cannabis use, and the relationship between low socioeconomic status and change over time in cognitive function test results were weak in this particular data set.

Even if the association is real and causal there could still be explanations that don’t involve brain toxicity.  For example, imagine that people who enjoy being stoned are less likely to choose jobs and recreational activities that are cognitively demanding.  They would then to some extent tend to end up scoring lower on cognitive function tests in later life.  This, if it were true, would be an explanation that does depend on the properties of cannabis, but not on toxic effects.

Over all, this result doesn’t have huge implications for drug policy.  It doesn’t change the basic fact that cannabis is far from innocuous but is also much safer than alcohol or tobacco.  It doesn’t affect the relevant international treaties and probably won’t shift domestic public opinion.  Differences of opinion on cannabis policy questions depend mostly on different preferences, and partly on other uncertainties. For example, would legal cannabis lead to more or less alcohol consumption?

I’d recommend the book “Marijuana legalization: what everyone needs to know”.  This is written by a group of public-policy academics, who have varying policy preferences, but looked at what evidence they could agree on. It gives a series of questions and what is known about their answers. Unfortunately it’s not (yet?) in the Auckland city library.

Links: Stuff, Science Media Centre

Nate Silver joins Google’s Chief Economist Hal Varian to talk about his new book “The Signal and the Noise: Why So Many Predictions Fail-but Some Don’t” and answer Googler questions.

Stuff thinks so, but actually it’s hard to say.  The statistics have recently been revised (as the paper complained about in April).

The paper, and the Labor spokewoman, focus on the numbers of deaths in 2008 and 2011: 18 and 27 respectively.

The difference between 18 and 27 isn’t all that statistically significant: a difference that big would happen by chance about 10% of the time even assuming all the deaths are separate cases.  It’s pretty unlikely that the 50% difference reflects a 50% increase in domestic violence, but it might be a sign that there has been some increase. Or not.

The Minister doesn’t do any better: she quotes a different version of the numbers, women killed by their partners (6 in 2008, 14 in 2009, 9 in 2011), as if this was some sort of refutation, and points to targets that just say the government hopes things will improve in the future.

There’s no way that figures for deaths, which are a few tenths hundredths of a percent of all cases investigated by the police, are going to answer either the political fingerpointing question or the real question of how much domestic violence there is, and whether it’s getting better or worse.  It’s obvious why the politicians want to pretend that their favorite numbers are the answer, but there’s no need for journalists to go along with it.