How To Teach the Law of Diminishing Marginal Utility in Economics

Here's How:

1. Get a package of fun-size candy bars.
2. In class, before introducing the idea of utility (satisfaction), get volunteers who say they would like to eat something with chocolate and peanuts in it.
3. If there is more than one volunteer, have them choose a number between one and 100. Whoever is closest to your chosen number gets to be the volunteer.
4. Place a desk in the front of the room facing the audience and have the student sit in it.
5. Explain what utility means to the entire class.
6. Draw a graph on the board, labeling the vertical side 'Utility' and the horizontal side 'Number of Candy Bars Consumed'.
7. Place the numbers one to 10 on the vertical side of the graph.
8. Explain to the volunteer that they are to eat one candy bar and then rate the utility they receive from one to 10. (10 is the highest utility)
9. After each candy bar is consumed, have the volunteer rate their satisfaction and place a point on the graph that represents this.
10. Continue until the student's satisfaction begins to drop. It is up to you how far you want this drop to go to prove the law.
11. Thank the volunteer (and allow him/her to go get a drink of water.)

Tips:

1. It can be expensive to take the students' utility all the way to zero.