Diagnose Falling Sales per User at Amazon While Monthly Active Users Keep Growing

You are a product manager at Amazon. Over the last six months, Amazon's monthly active users (MAU) have risen steadily, which looks like strong engagement. Over the same period, though, average sales per user have kept falling. What could explain this combination, and how would you work out which explanation is correct? ```hint Treat the metric as a ratio Average sales per user has a numerator and a denominator. Before naming causes, ask which of the two moved, and whether the growth in active users brought in people who behave differently from existing customers. ``` ### Clarifying Questions - Does "sales per user" mean revenue, orders or units per user, and is it divided by all monthly active users or only by those who bought something? - What counts as a monthly active user: any visit to the store, a signed-in session, or activity in any Amazon app or service? - Over the six months, has total sales risen, stayed flat or fallen? - Is the decline broad, or concentrated in certain countries, product categories, platforms, or groups such as new versus long-standing customers? ### What a Strong Answer Covers - Checking metric definitions and measurement for changes in either the numerator or the denominator - Decomposing sales per user into components (share of actives who buy, purchase frequency, order value) and finding which one moved - Separating a change in user mix brought by the new actives from existing customers genuinely buying less, using cohort and segment cuts - Concrete internal and external causes, each tied to the evidence that would confirm or rule it out - Judging whether the trend actually hurts the business, and the actions and success metrics that follow ### Follow-up Questions - Suppose total sales rose over the six months even as sales per user fell. Is that a problem, and how would you explain it to leadership? - The decline turns out to come almost entirely from users who became active during the six months. What would you do to turn them into buyers? - What would you track alongside sales per user so that healthy growth in active users is not mistaken for decline?