Could plastic bag use rise 40% in one year?

Media reports this morning are claiming that a ‘confidential draft report’ to the federal government shows that plastic shopping bag use soared last year:

Bag use dropped steadily to 3.36 billion a year in 2006, but spiked back up to 4.84 billion in 2007, the report said.

Now I can think of at least one reason that this report is ‘draft’: that number fails a basic ‘does it look right?’ test. Despite the active efforts of retailers to reduce plastic bag use – supermarkets with their canvas bags, other retailers switching back to paper – and consumers declining additional bags when a new item can go in an existing bag, per capita use actually increased 40% in just one year?

The people writing that report would need a very good theory to explain that before I would believe it. The most obvious explanation I can think of is that either or both of the 2006 and 2007 figures are wrong.

Such a shonky set of numbers is worthy of re-opening my old Catallaxy-era ‘dubious research’ category.

13 thoughts on “Could plastic bag use rise 40% in one year?

  1. People need to be reminded that a major reason for concern about plastic bags (killing marine life) has been seriously called into question. If the “killing marine life” story turns out to be a furphy, what is the reason for any kind of concern about the use of plastic bags?


  2. I agree it looks very dodgy. However the news story claims to disclose figures about the tonnage of plastic bags imported (which allegedly accounts for most of them) and they should be easy enough to check. Maybe the category definition has altered and now includes bin liners or something.


  3. Ken – My use of large rubbish bags is certainly higher, as I no longer have supermarket carry bags I can use. I expect that is also true of many households, so we would not expect reduced shopping bag use to translate into equivalent total reduction in bag use. But that could not explain an *increase* in bag usage.


  4. I’m with Rafe. This is pure enviro-religion. The only way I can think of that the number of bags could have gone up *at all* is that supermarkets somehow massively increased the use of multiple bags for reinforcement when bagging heavy items. But a 40% increase is nonsense.


  5. I don’t think its enviro-religion — I think its just politics –there are far more serious environmental concerns than plastic bags. I’m sure on a list of worries, plastic bags must way down the list.


  6. If it feels wrong, it probably is wrong.
    Someone has leaked this so it reflects a fight in the bureaucracy.
    Any ban will be wildly unpopular and it would be very surprising if Rudd spends so much goodwill on a low order issue like this.
    So I guess Garrett and those sympathetic to him are scrambling to stay in control of the issue.
    It will be fun to watch.


  7. The politicians are presumably into it for the politics, but the enviro-mums are in it for the ‘sacrifice’.

    Rudd’s team are good at this kind of distraction. The ‘alcohol violence crisis’, the ‘homeless crisis’ and anything else they can find. It’s politically pretty savvy.

    It’ll be interesting to see how they handle the larger and more expensive issue of carbon emissions. Presumably by promising something for another government in the future. the Blair/Brown government’s response. Hopefully they’ll read some Bjorn Lomborg.


  8. Andrew, I’d normally agree with you on using the “does it look right?” test on these numbers.

    However, one input into a theory behind these numbers is that the Australian Retailers Association Code of Practice for the Management of Plastic Bags expired at the end of 2005. This code ( ) aimed to reduce use by 50% by 2005 through retailers undertaking consumer awareness campaigns, promoting re-usable bags and staff training. I don’t think they were obliged to actively do anything after 2005.

    Still, a 40% rise in one year is pretty big – but it just returns per capita use in 2007 (on these reported numbers to 230 each) the same level as in 2004 (about 235 per person).

    What does all this mean? In spite of greenie propaganda about almost non-existent impacts on sealife (greenmail) and government intervention (greentape), industry self -regulation (greenwash) does the wise old Australian consumer actually like plastic bags?

    Based on the numbers in the article and previously published figures plastic bag use in Australia from 2002 to 2007 would be about:

    Year bags (billion)
    2002 5.95
    2003 5.2
    2004 4.7
    2005 3.9
    2006 3.36
    2007 4.84

    One theory: the numbers are right but the evangelists who run plastic bag policy are trying to whip up hysteria?


  9. Procrustes – I’m sure the envangelists who run plastic bag policy are trying to whip up hysteria, but unless they are fabricating the numbers that can’t explain a 40% increase (and you would think the the rational propagandist would think up a more plausible increase than 40%). And if that code of conduct expired in 2005, why was there another big drop in 2006, followed by a surge in 2007? Maybe it is just the inner Melbourne market, but the supermarkets in my area are still actively working to reduce plastic bag use, with the canvas bags prominently placed neared the check outs and staff asking if customers want a bag when they only have a small number of items.

    I can’t find this latest report on the web, but it’s clear that the earlier numbers are pretty dodgy, using such methods as extrapolating numbers of bags from bag imports as measured by tonnage. This creates obvious problems in when the imports arrive – if for example a large shipment that would normally have arrived in December 2006 instead arrived in January 2007 that would help explain why 2006 was low and 2007 high, with no implications for actual bag consumption.

    Also, it requires an estimate of bag weight. If as is likely the light bags used by supermarkets are declining as a % of all bags the average weight of bags should be increased, leading to a lower total number of bags in the estimates.


  10. I don’t know about the rest of the country but I never see anyone else use green bags in either Coles or Woolworths in Broome. I suggest that the best incentive would be a rebate rather than a charge for not using plastic bags. It’s over to the big 2 really. The 40% drop off is easily explained as the initial campaign has all but disappeared.


  11. Kevin,

    they’re quite popular in some parts of Melbourne (yuppie environment syndrome — the 15.0L/100K Toorak tractor is fine but the bags arn’t — I doubt this exists in Broome), and some places would like to phase them out completely. I’m in the same position as Andrew in that if they don’t give them to me at all (I collect about 50% of my groceries with them — the rest go into my backpack), I’m just going to buy them for my rubbish anyway.


  12. If it’s a choice between people using their biodegradable shopping bags for their household bin rubbish and buying non-biodegradable bin liners, it makes more sense to encourage the use of disposable shopping bags than discourage them.

    A far more productive target for the reduction of plastic waste is in the packaging industry: so many things are wrapped in heavy plastic shells, contain superfluous non-degradable or recyclable plastic bags, and are then placed in boxes. So unnecessary.


  13. Andrew

    I agree the quality of these numbers is not brilliant. But the particular problem you allude to (lumpiness of import data) would apply whether it was tonnage or bag numbers. Also, the previous data were built up from both imports (about three quarters of bags) and local production (about one quarter), so there is less scope for this being an issue.

    I also agree that there are incentives for these numbers being unreliable – but I still maintain that there expiry of the industry code would be a reasonable explanation for some turn around in the decline (and I do agree that forty percent growth is still a whopping turnaround).

    I wonder whether composition is a factor. The original report assumed 5.5g a bag. The ten bags I had in my pantry tonight weighed an average 8g each. So if my (major supermarket) bags were more representative of bags used by Australian we would be using 3.3b now, not the 4.8 they estimate. And if 8g was more representative in 2002, we would have used 4b not 6b bags. Plenty of room for composition effects to distort the trends.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s