Ringelmann effect
the tendency for groups to become less productive in terms of output per member as they increase in size. The effect is named for Max Ringelmann (1861–1931), a French agricultural engineer who studied the productivity of horses, oxen, men, and machines in various agricultural applications. He found that groups often outperform individuals but that the addition of each new member to a group yields less of a gain in productivity. Subsequent studies suggest that this loss of productivity is caused by the reduction of motivation experienced in groups (social loafing) and the inefficiency of larger groups.