Rubbish statistics about rubbish

I saw an article in the Daily Mail today (read for research purposes only I hasten to add) about how much waste is clothing.  They called it the Primark effect.  The article claims that “Throwaway fashion that cannot be recycled now makes up 30 per cent of the waste in council tips”.  In more detail it notes that “Five years ago [textiles] constituted 7 per cent of the waste stream. Now it is up to 30 per cent by weight”.  Not just the Daily Mail by the way.  It’s also in the Telegraph, Marie Claire.  The Independant had an article a year ago that did not have this amazing 30% claim.

30% sounds such a high number that I am forced to stop and think.  And, I’m not even drawn to the difference between textile waste overall and ‘throwaway fashion that cannot be recycled’.  So, can the waste volume be 30%?  Has this volume quadrupled in four years?  Even 7% sounds much higher than I’d expect.  The factor of four sounds a much much larger move than can possibly be explained by trends in purchasing.  My hunch is that it’s much more likely to be changes in recyling volumes and trends.  I feel compelled to check to see whether it’s real or just nonsense statistics.

The waste tip mentioned is in Croydon, so it seems sensible to start there.  What’s changed over time – well, for a start, from March 2008 Croydon started kerb-side collection of garden waste.  I’m not sure how much volume this removes, but having been to the local tip quite a few times, my guess is that in the summer it could be quite material.  This on its own will drive up the percentage of other types of waste – not because the volumes are going up, but that the volumes overall are going down (it’s called the denominator effect, and would be a really basic miss).  So, how material could the denominator effect be?  Well, if we look at what it in bins at households then whether for waste bins or recyling bins the volume is tiny at 1-1.5% (see diagram below, thanks to the BBC).  The 30% is far from view, showing how relatively small moves in the volumes of other products shifted from council tips to recycling bins could have a massive swing effect on the relative amount of textiles.  :-

Continuing the look at overall volumes, a DEFRA report on municipal refuse in 2007 shows that the total of all misc non-combustable waste and other waste came to 15% – this would include textiles (I think).  Once again, far far from the 30% quoted.  But that same report shows that garden waste accounts for more than a quarter of waste, even though I’m guessing that quite a few areas now have garden waste kerbside collection.  So, is Croydon I did assume that even though it was an innner-city council that Croydon would have made some material movement … However, when I look at the Audit commission data for Croydon it shows up spectacularly badly, having a landfill percentage that has moved from 87% in 2005 to 80% in 2007 – moving it to the second worst of all councils shown in 2007 (see below).chartimage_000808

The intruiging thing here, is that the move isn’t large enough to explain the move in Crodon’s refuse by denominator effect since the denominator can’t have moved enough (I admit I’m surprised – I did expect that to be a material issue).  I could give up here … but on a moments reflection, the skew is the wrong way around.  The overall statistics show other councils as doing much much better on recycling, and the textiles being talked about aren’t recyclable.  So, we should have expected Croydon to have LOWER textile figures than normal, not higher.  And the earlier stats from DEFRA would show Croydon as reporting figures at least twice as high as average.  So, there is something else going on.

I’ve dug quite a bit more, but can’t find anything to get a definitive handle on what the statistic should be.  And, this dig has taken quite long enough already.  But, as a close, I do have the total clothing bought in the UK each year, at 2 million tonnes in 2006.  And, the total UK landfill which has moved from 22.6 million tonnes to 16.9 million tonnes between 04/05 and 06/07 (See here).  That would point to a percentage of about 9% in 04 (surprisingly close to the 7% quoted, if all clothing was landfilled – it could even be right!).  And, if the clothing figure had stayed unchanged the denominator effect alone would take that to 12%).  But clothing purchases would need to have more than doubled by weight in the last 2 years to get to 30%.  And, as a last thought – to reach 30% then one skip in three in a council dump would need to be ful of textiles … and it clearly clearly isn’t.  In short, though I haven’t managed to get to the truth, every thing I’ve seen shows that 30% to be as fishy as I first thought.

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This entry was posted in Cognitive biases, Musings, statistics. Bookmark the permalink.

One Response to Rubbish statistics about rubbish

  1. Pingback: repost : Rubbish statistics about rubbish « Dodgy thinking

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