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An Evaluation of the Plastic Bag Levy: Part 2

27th February 2017

Part One of this blog series evaluating the plastic bag levy in the UK examined the data available through the government website, concluding that one of the stated aims of the policy has been achieved. From this, media sources have praised the levy as removing billions of plastic bags from circulation and as having a “huge impact” in starting to stop the negative consequences of bags in the environment. This second post considers the evaluation criteria used and the limits to any conclusions which may be drawn from this.

Thus far, the public evaluation of the policy has relied upon data regarding sales of “single-use plastic bags” (defined as those 70 micros thick or less), from seven supermarkets. It would be surprising if this is the only metric used to evaluate the policy, but it is the only one made public and used in public evaluation. The supermarkets considered are, without doubt, some of the most significant contributors to plastic bag wastage, but they do not represent the full spectrum of retail contexts in which bags are used (or sold). This means the data set can only be considered indicative of a trend in the supermarket context.

The focus on single-use bags also only considers one type of plastic bag sold by retailers, not quantifying the knock-on effects on sales of re-useable bags. It is highly likely that sales of re-usable bags have increased, and there seems to be a tacit assumption that this is a positive thing without any questions made about how these “re-useable” bags are (re)used. It may be that consumers are purchasing re-useable bags and using these in the supermarket and other retail contexts each time they shop. This may be occurring to the extent that there is a huge reduction in sales of all plastic bags and a large drop therefore of the environmental cost of retail bags.  However, there is no evidence that consumers always re-use bags, and it may also be the case that “re-useable bags” are sitting on selves and in cupboards in consumers’ homes awaiting further use.

Supermarket Check-out

A further key assumption in this which has not been challenged is whether “single-use” carrier bags are, in practice, “single-use”. This, again, is an unacknowledged assumption but appears present in the choice of “single-use” bag sales as the evaluation criteria. Previously, “single-use” bags may have found use as a bin bag, or for transporting swimming kit for example, but this is not reflected in their raw sales. As a secondary consequence, alternative means will have to be found for these bag uses but this is not considered in the data provided. Returning to the stated objectives of the policy, this may reduce the number of a certain type of bag being visible in the environment, but may have negative knock-on consequences in the increase in production of bin bags, for example. And even without considering secondary consequences, the evaluation employed is unable to assess the levels of bags present in the environment. Although this is somewhat unsurprising given the data was gathered over the initial six month period, disconnect between the objectives and the evaluation data remains.

This is not to say that the levy has not had some success; sales of single-use bags have clearly fallen, and it would seem that shoppers are adopting alternative strategies for carrying their shopping.  It is also not to say that the levy cannot be an initiation point for greater action and change in household waste.  But, the evaluation thus far seems limited in depth and extent making conclusions difficult to draw. This in itself seems linked with the limited but specific scope of the objectives of the policy which is to reduce use of “single-use bags” and their associated litter. Of course it would be impractical to consider all knock-on consequences, but as more analysis becomes available and more policy is introduced, a better evaluation will be possible.