"We were unable to find evidence that any sugar tax actually implemented anywhere in the world has led to improvements in health"

It cannot be said too often that sugar taxes have not reduced obesity anywhere in the world, and it is not for want of trying. Many places have experimented with taxes on sugary drinks, in particular, but the impact on calorie consumption has been trivial to non-existent. Naturally, therefore, they have had zero impact on obesity.

Most politicians don't care what the evidence says. Sugar taxes raise revenue and that is enough for them. If they want to portray sugar taxes as a health measure, they can always point to theoretical models created by sugar tax advocates which claim that a tax of 10 or 20 per cent will lead to x fewer cases of obesity.

But the real world evidence is clear. They don't work because consumers will tend to pay up or switch brands or switch to other sugary products. In any case, the proportion of calories they get from soft drinks is small to begin with.

The 'public health' lobby are bluffing. They tend to get away with claiming that there is 'overwhelming evidence' for policies which have weak or conflicting evidence behind them and, as we have seen with minimum pricing, politicians are often unable to distinguish between modelling from advocates and evidence from the real world. 

But in New Zealand, the government did bother to look at the evidence and commissioned the respected New Zealand Institute of Economic Research (NZIER) to review it. NZIER reviewed 47 studies and this is what they said:

The evidence that sugar taxes improve health is weak.

Moreover:

Our conclusion is that the evidence base gets weaker further along the chain of intervention logic. If taxes did not have economic costs, through deadweight losses and implementation costs, then even a slight causal link between a tax and an improvement in health outcomes might be justified. That, however, is not the case

NZIER's full report was published at the end of January and is worth reading. It is a sober and rational assessment. By contrast, the response from a leading Kiwi nanny statist, Boyd Swinburn, was a predictable rant about 'merchants of doubt'.

The 'public health' racket is in such a sorry state that ad hominem attacks have increasingly become its only weapon. Unable to find any ties between NZIER and Big Sugar, Swinburn resorts to the soft smear of complaining that a government-funded report written by impartial economists could be useful to those who oppose sugar taxes - and, in Swinburn's cartoon world, only nasty corporations oppose sugar taxes.

Science historians Naomi Oreskes and Eric Conway coined the term Merchants of Doubt in their expose of how Big Tobacco and Big Oil paid scientists and conservative think-tanks to dispute the scientific evidence on tobacco harm and climate change. Doubt in the evidence was the "product" they were marketing to avoid government actions which might threaten big business profits.

A health levy on sugary drinks, with the money going to prevention, is the new target. As expected, Big Food and Beverage and business interest groups are the leading merchants of doubt but conservative politicians and economists steeped in last century's economic theories are joining their ranks.

God knows what 'last century's economic theories' are. Perhaps he is referring to things like price elasticity, substitution effects and the concept of regressive taxation?

I'm tempted to fisk the whole of Swinburn's article, but what's the point? If you read it, you will see the double standards, sleight of hand and misdirection fly off the page. It is not exactly subtle.

But you may want to also read NZIER's Laurie Kubiak's response. The following is, I think, the key point:

The framework looks at why a tax on sugar taxes might be effective, by asking "by what process would a tax on fizzy drinks lead to improvements in health?" This is not a simple matter when it comes to sugar in drinks (as opposed, say, to tobacco), because there are many high-sugar substitutes to fizzy drinks that are not taxed in most countries. If a tax on drinks simply induces a switch to chocolate, for example, then health outcomes might remain unchanged.

We think that to be effective at improving health, a sugar tax must work across five steps: it must increase price, the increase in price must cause consumption to fall, reducing consumption must lead to a lower sugar and/or energy intake, the lower energy intake must result in lower physiological risk factors and lower physiological risk factors must improve health outcomes.

... We found that the evidence for effectiveness became weaker the more steps in the logic were included in the study. It is possible a sugar tax may lead to some reduced consumption of the taxed product in some contexts. However, we found no studies based on actual experience with sugar taxes that identified any resulting impact on obesity, diabetes or other health outcomes.

And the take-home message is, as always:

We were unable to find evidence that any sugar tax actually implemented anywhere in the world has led to improvements in health.