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BCG gave me a market sizing and I completely panicked on the assumptions
- Market Sizing
I had a market sizing in an interview and the structure itself was okay, but once I got into assumptions I felt lost. I kept second-guessing whether the numbers were reasonable, which made the whole thing much slower than it should have been. How do people get better at making assumptions confidently without sounding like they are just making things up?
The key is to remember that assumptions are not judged on exact precision. They are judged on whether they are reasonable, transparent, and internally consistent.
What do you do when you don't know a market-sizing input?
- Market Sizing
In market sizing I sometimes get stuck because I genuinely do not know an input, like average store traffic or household spending on a niche product. Are you supposed to ask the interviewer, make an assumption, or find a different way to structure the estimate?
Do not freeze just because you do not know a real-world fact. State that you do not know the exact figure, propose a reasonable assumption, and explain the logic behind it.
Bottom-up vs top-down market sizing: which should you use?
- Market Sizing
I understand the definitions, but in a real case how do you decide whether to size a market top-down or bottom-up? Is one approach viewed as stronger in interviews, or is it just whichever gets you to a reasonable answer faster?
Neither method is automatically better. The stronger approach is the one that fits the information available and lets you explain the market logically.
How do you make assumptions in market sizing without sounding random?
- Market Sizing
My biggest issue with market sizing is not the framework. It is the assumptions. I always worry the numbers I choose sound arbitrary, so I end up hesitating too much. What is the best way to make assumptions feel more grounded?
Try to base assumptions on simple reference points instead of isolated guesses. Population ranges, household size, usage frequency, and comparable categories are all examples of anchors that can make your logic feel much more credible.