Market Sizing Drill
Nobody in the room knows how many cups of coffee America sells in a day, the interviewer included. What is being graded is whether you can take a question with no available data and turn it into four or five factors a stranger could follow. So this drill makes you build the chain under a clock, then puts it next to a reference chain so you can see which term carried your error.
Six cases across consumer markets, physical counts and platform volumes. Landing within a factor of three is a good answer.
How many cups of coffee are sold in US coffee shops on a typical day?
Answer in cups per day
Build the chain
Start the clock, then add one factor at a time: name it, give it a number, and choose whether it multiplies or divides the running total. Lock it in when you are done, or let the clock do it for you.
Your chain then lands next to a reference chain: one defensible route to the answer, built from the anchor numbers, not an official figure. Compare the two term by term. That is where the learning is.
What good sounds like
- Say the units at every step. The single most common way a chain lands twelve times out is multiplying by a monthly figure and then by twelve months, or dividing a stock by a rate. If you narrate the units, you catch it live.
- Anchor on something you genuinely know. Population, households, GDP, an average salary. Never anchor on a market size, because that is what you were asked to produce.
- Cross-check from the other direction. If you built it bottom-up from people, check it top-down from spend. Two routes agreeing is worth more than either route being precise.
- Flag your weakest term unprompted. Saying “the one I am least sure of is average spend, and if it is half my number the answer halves” is the sentence that separates the top decile.
- Round hard. 54m, not 54.3m. Precision you did not earn is a tell, and it slows the arithmetic down when the clock is running.
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