According to ergodic theory, you are allowed to use a group average to make predictions about individuals if two conditions are true: (1) every member of the group is identical, and (2) every member of the group will remain the same in the future.10 If a particular group of entities fulfills these two conditions, the group is considered to be “ergodic,” in which case it is fine to use the average behavior of the group to make predictions about an individual.
