Back-of-the-envelope sizing of how many users Amazon acquires per day

Estimate the number of new users Amazon picks up in a single day. Explain how you structure the estimate, label each assumption, and finish with a figure and a sense of how confident you are in it. ```hint Stock or flow Decide whether to work from a stock (how many customers Amazon has and how fast that base turns over) or from a flow (how many people enter the pool of possible shoppers each year and how many of them start buying), and pin down what makes someone a new user before you pick any numbers. ``` ### Clarifying Questions - Is a new user a newly created account or a person making a first purchase, and does someone opening a second account count? - Worldwide, or a single country such as the US? - Only the online store, or also people who start with services such as Prime Video, Kindle or AWS? - An average day across the year, or a peak day during a major sale or the holiday season? ### What a Strong Answer Covers - A definition of "new user" and a stated scope, settled before any arithmetic - A top-line equation that turns a yearly flow or a customer stock into a daily count - A breakdown that reflects where new users actually come from, with labeled, round assumptions and a rationale for each - Correct, unit-consistent arithmetic ending in a daily figure with a range - A sanity check from a second angle and the sensitivity to the shakiest input ### Follow-up Questions - How would the number differ on a major sale day or during the holiday season, and why? - If you were the PM responsible for growing this number, which inputs in your equation would you try to move? - What data would you ask for to check the estimate, and which assumption would you test first?