A club president discovers that contributions of club members drop when the total contribution of all members is published rather than the contributions of individuals. This drop can be explained by the phenomenon of.

This drop can be explained by the phenomenon of social loafing.

Explanation:

Social loafing is a term in social psychology used to describe a phenomenon that takes place when individuals work in groups. It refers to a tendency people in general have of making less effort when working with others than they would while working on their own.

Social loafing offers an explanation as to why groups can be less efficient and less productive than individual work. It is as if people feel they do not need to put in as much effort as they would normally simply because they are aware of the efforts others are making.

That could also explain the drop in contributions described in the passage. Upon seeing the total contribution of all members, individuals will understand they do not need to contribute as much. Their effort is not being distinguished from the group effort. On the other hand, if the contributions of individuals are published, their effort will be acknowledged individually, which serves as motivation.