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Market Sizing - Guess the number of rats sold in the US?

Guessestimation Guesstimate Market sizing
New answer on Dec 31, 2021
3 Answers
2.8 k Views
Anonymous A asked on Oct 18, 2018

I found this question difficult to tackle. Even though I could segment the possible channels where rats are sold, estimating the number is really difficult. Would love to hear answers from everyone and understand how to tackle such unconventional questions.

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Dennis updated an answer on Oct 18, 2018

This seems like an interesting one as you could actually make the discussion quite extensive. So this is how I would go about it (if this does not make sense I'd gladly be corrected):

At the moment I can see four different market segments for rats:
- Education
- Research (univeristy labs and companies)
- Pets
- Food (for other pets)


I will just do this one for now, maybe you can think of the others yourself. There is a lot of assumptions here, but I think the main point they want to see is that you can get to a number by logical reasoning. This number could be way off in reality.

With education I assume that biology and medical students at universities will dissect animals as part of a course. Let me assume that the percentage which has to dissect an animal of biology students is 100% and medical students 50%. At my university, of the 20,000 students about 3,000 are in medicine and 1,000 are in biology. This makes 2,500 animals being dissected for education at my university. Let's assume 20% of that are rats, so 500 rats being dissected. I will assume that the rats/student ratio of 500/20,000 = 2,5% is constant throughout the country. Let us assume that there are about 20 million university students in the US. By these students collectively, 500,000 rats will be dissected during their studies. Assuming the average university study period to be 4 years, this amounts to 500,000/4 = 125,000 rats per year.


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Anonymous replied on Oct 18, 2018

Great answer by Denis.

The purpose of these questions is to somewhat throw you off balance and see how you react. The actual answer is much less relevant - I doubt that anyone knows the actual answer. The key is how you get to that answer...

So if you tackle the problem like any other market sizing, you'll be fine. So Structure, structure, structure... Denis has given a great example. Pick halfway thought-through assumptions and off you go...

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replied on Dec 31, 2021
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Hi there,

Providing some market sizing thinking for anyone revisiting this Q&A:

Remember that there's rarely a "best" answer with market sizing. What's important is that you break down the problem the way it makes sense to you. Importantly, break it down so that the assumptions you make are the ones you're most comfortable in.

For example, do you know all the major brands? Great go with that. Do you understand all the segments of that country's population (either age or wealth or job breakdown)? Go with that. Do you know the total market size of the tourism (or hotel) industry? Then break it down that way.

Some tips:

  1. Just like in a case, make sure you understand the question - what are you really being asked to calculate
  2. Decide whether a top-down or bottom-up approach is best
  3. Figure out what you know you know, and what you know you don't know, but could estimate
    1. This helps you determine how to split out buckets
  4. Stay flexible - you can start with a "high-level" market sizing, but gauge your interviewers reaction....if it looks like they want you to do more...then go along level deeper in terms of your splits
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