In the second round, an additional student is added to the game. The 2 students have 30 seconds to transport as many balls from one container to the other. In each successive round, an additional unit of labor is added, allowing us to calculate the total, average and marginal productivity of labor. The graph below represents the actual results from the experiment.
Diminishing marginal product set in with the addition of the 3rd worker; however, with the 4th unit of labor, the students came up with a different strategy to form running lanes and actually experienced an increase in MPL. With the addition of the 5th unit of labor, MPL decreased again. This is a fun and easy way to demonstrate the concept of diminishing marginal product.