Why do some cohorts have less than 100% <1 week retention?

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To answer this question, let's look at the relevant information from the knowledge sources:The reason some cohorts have less than 100% <1 week retention is related to how Mixpanel calculates retention and the nature of user behavior. According to the <https://docs.mixpanel.com/docs/reports/retention#basic-features|Mixpanel Docs on Retention>:1. Retention counts unique users, not event totals. Each user cohort bucket includes every unique user that performed the "A event" criteria in that time window.2. The first column (Date) indicates when the user performed the "A event". The Size column shows the number of users that performed the "A event" within that time period.3. A customer can only be counted once per bucket, but can be included in more than one bucket if they perform the "A event" in multiple time periods.Given this information, it's possible for cohorts to have less than 100% <1 week retention because:1. Some users may perform the "A event" (e.g., sign up or first use) but not return to perform the "B event" (the retention action) within the first week.2. The retention calculation is based on unique users performing specific actions, not just logging in or being active in any way.3. Users who perform the "A event" late in a given time bucket may not have a full week to perform the "B event" before the next bucket starts.It's important to note that retention is not the same as a funnel, and it measures recurring behavior rather than a linear progression of events. This means that even within the first week, some users may not exhibit the desired retention behavior, leading to less than 100% retention.

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