Much of (micro)economic theory is based on the following ideas. People make conscious choices. These choices depend on what these people want. People typically want, keeping all else the same, more money. To quote (in a rough translation) a popular Austrian comedian, Alf Poier, on this matter: “I quickly realized that money is quite valuable and doesn’t take up much room.” This also means that in order to get more money, people would be willing to give up other things that they want.
And we just saw an incredible demonstration of that with the UK-wide introduction of a 5p charge for every plastic bag in essentially all supermarkets from the beginning of 2016. The effects of this policy have started to become evident. It seems that the introduction of the 5p charge for every plastic bag has reduced plastic bag consumption in supermarkets by roughly 80%.
What I find most impressive about this is that 5p for a plastic bag does not seem a lot of money and I usually argue that people typically try to get the big decisions right, but will not spend too much time thinking about small impact decisions. And here we have a comparison between two very small things: the loss of 5p versus the discomfort of having to bring your own bag to the shop. And yet, this had such a tremendous effect, with the discomfort of bringing your own bag valued less than 5p by most people most of the time.
As shopping is an almost daily activity for most people, I guess, one could see this as a decision between the loss of 5p per bag every day in a whole year (worth approximately 36 pounds assuming you use two bags every day) versus adopting a general policy of bringing a bag (or two) to the supermarket whenever you go shopping (which maybe requires a mental effort only a few times before the taking of bags to the supermarket becomes an almost automatic, that is mentally costless, behavior).
Nevertheless I do find the 80% reduction in the use of plastic based on such a small charge a remarkeable example of the forces of basic microeconomics at work.