CUME metrics in Webcast Metrics cannot be accumulated and summed to create an aggregate CUME report. In other words, you cannot take several related CUME results and add them together to reach a CUME “total” for the group.
For example, you cannot add CUME for iPhone and CUME for Android together to reach a valid CUME for mobile calculation. Similarly, you cannot add CUME for Vermont and CUME for all the other New England states together to reach a valid CUME for New England total.
Here’s why: CUME is defined as the “Number of unique listeners with at least one active session in the reported time period.” However, in the real world, a certain percentage of listeners will fit into more than one category within that time period. In such cases, the listener’s CUME value is “1,” but if you summed their reported CUME you would get “2” or more (depending on circumstances), which is incorrect.
Below are some examples that show how summing CUME would create inaccurate reporting.
Case 1
Listener A listens to a live stream every morning while eating breakfast. If you did a CUME report for a week you would see:
Listener A on Monday: 1
Listener A on Tuesday: 1
Listener A on Wednesday: 1
Listener A on Thursday: 1
Listener A on Friday: 1
Listener A on Saturday: 1
Listener A on Sunday: 1
The true CUME for listener A for the week is “1” because that is the listener’s value as a unique listener with at least one active session during that one-week period. But if you summed the days, listener A's accumulated value would be “7,” which is incorrect as a CUME report.
Case 2
Listener B is a delivery driver. She starts the day by loading her truck in Albany, New York. 90 minutes later she makes a delivery in Springfield, Massachusetts. An hour later she makes a delivery in Brattleboro, Vermont. Two hours later she unloads in Manchester, New Hampshire. She has listened to the same audio stream during the course of her day, during which she has been in four different states. Her reported CUME activity for the day is:
Listener B in New York: 1
Listener B in Massachusetts: 1
Listener B in Vermont: 1
Listener B in New Hampshire: 1
The true CUME for listener B is “1” because that is her value as a unique listener with at least one active session on that day. But if you summed her reported CUME activity by state, it would add up to “4,” which is incorrect as a CUME report.