ADAM SMITH remarked that no dog ever made a free and fair exchange of one bone for another. Many pooch-owners will agree, having spent frustrating minutes trying to wrestle a stick or a ball off their pets.

But humans are supposed to be rational. They should not value things they own more highly just because they already possess them. Experiments in the classroom have shown, however, that people may be subject to this trait, dubbed the “endowment effect”. In a classic study, students were randomly given a mug. Those who received the mugs were asked what price they would sell them for; the mean was $5.78. Those who did not were asked what they would buy them for; the average was $2.21.

In a similar test, students were asked to state their preference between a mug and a chocolate bar; 56% favoured the former and 44% the latter. Two other groups of students were then randomly assigned the mug or the chocolate and then asked whether they were willing to swap; in each case, around nine in ten of the students were unwilling to do so. You might say they were “possessed”.

That is the kind of result that gets behavioural economists...Continue reading