Planet Money’s Dec. 25 podcast was another episode that was too good not to blog. They perform a classroom experiment related to gift-giving: randomly distributing ten different treats to a classroom of seventh-graders. Each student received one snack, which ranged in desirability from raisins and Fig Newtons to Three Musketeers and Sour Patch Kids.

Upon initially receiving their gifts, the kids gave an estimate of how much they liked what they received on a scale from 1 to 10. The total utility of the class at this stage of the experiment was 50. It took about 11.8 seconds for one of the middle schoolers to suggest that they could all be better off by trading. After one minute of swapping, the class’s utility went up to 82.

Economists are used to this sort of thing, but take a minute to appreciate how significant this is. The students’ assessment of how…