In praise of plastic

By Eric Crampton 14/07/2015


The Dom Post wants to tax plastic bags. In doing so, they advance what has to be among the sillier counter-arguments to a study.

The Dom writes:

Just why does a small levy, of perhaps five or 10 cents a bag, typically have such a big effect on behaviour? A study by Argentinian researchers in 2012 found that one group of shoppers disliked the new levy but started using their own bags because of the cost. But another group of shoppers supported the charge for environmental reasons. The new charge forced customers to think again about their behaviour. It was a nudge to change their usual habits.

The plastic bag advocates have one surprising argument: using your own bags repeatedly can kill you. A 2012 study by George Mason University found that the switch to reusable bags was killing about five people a year in San Francisco, because their bags were left unclean and grew germs. Keeping meat and vegetables in the same bag is part of the problem. And leaving bags for long periods in the car boot provides a hothouse for bacteria.

The answer, of course, is to clean your shopping bags. There is a similarly short reply to those who say the levies are regressive, bearing more heavily on the poor. Low-income shoppers, like the rich, should switch to reusable bags.

San Francisco has about a million people across the greater region; scale it up five times over to get comparable New Zealand figures. Then recall that San Fran is one of the richest, trendiest, most health-conscious places in the world. If anywhere is going to be a lower bound for deaths caused by failing to clean mandatory reusable bags, it’s San Fran.

If the George Mason study is credible, which it will be since Jon Klick is one of the authors, then 20 deaths a year would likely be a lower bound for a complete ban on plastic bags. A tax will have less effect because it’s less likely to change behaviour.

So then. Tally up all the costs imposed on the environment by the existence of plastic bags in New Zealand. If those are less than the costs of 20 human deaths per year (at about $4 million each by usual cost-benefit rules here), then leave it alone. Seem likely that NZ plastic bags are costing the world $80 million a year?

I’m not a low-income shopper. But I totally use plastic bags. And then I re-use them as kitchen trashbags. I’d ignore the tax because I don’t care whether I add a buck to my shopping trip or not, and because I hate cleaning re-usable bags. Poorer folks might have to flip to using the re-usable ones. And they might not have the time to do the cleaning that prevents the dying.

“If they don’t like paying the tax for the plastic bag, let them use re-usable bags and wash them thoroughly”. Appropriate on Bastille Day.