Extra-long Market Sizing Question

Market sizing
Recent activity on Feb 07, 2018
6 Answers
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Andy asked on Feb 07, 2018
BA at a second tier consulting firm, preparing for upcoming MBB interviews

Just received an interview invitation from one of the top consulting firms. The HR mentioned that the market sizing question and the case would take half an hour each, while both interviews would have fit elements. Does that mean I should expect a half-hour market sizing case? That being the case, what should I do differently to stretch it to 30 min?

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replied on Feb 07, 2018
#1 Coach for Sessions (4.000+) | 1.500+ 5-Star Reviews | Proven Success (➡ InterviewOffers.com) | Ex BCG | 10Y+ Coaching

Hi Andy,

as mentioned, there is no need to worry whether you should stretch or not the market sizing for a couple of reasons:

  1. the HR person may have approximated the time – it could be less time for market sizing and more for fit, or you may have multiple market sizing
  2. most of the time, the interviewer will adapt to your performance, eg, if you are “too fast” will ask for further clarification, if you are “too slow” will give you signs you have to speed up, if you are fast and right will normally provide further market sizing. In my final at BCG I got two market sizing and one brain teaser – mainly as I managed to crack quickly the first market sizing assigned
  3. the key for a good market sizing is the actual structure, math and communication you will provide. Time is also relevant, but secondary to the previous ones, so far that you manage to find a proper solution in a reasonable amount of time (as mentioned, the interviewer will normally give signs of what he/she considers reasonable).



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Andy on Feb 07, 2018

Thanks very much! I'll just focus on a rational and appropriate structure. If the interviewer wants to do something funny, I believe that it's gonna be fair to all of his interviewees lol. You're right. Structure, math, and communication is still the key drivers of a Pass

replied on Feb 07, 2018
Former BCG Principal and decision round interviewer

I agree with other reply. I also believe that there might be a misuse of the word "market sizing" from HR side here, or the fact that what they call "market sizing" is way more deep than the classic brain teaser "how would you estimate the market for xyz in abc country?"

Either way, you shouldn't be worried about it, focus on interviewer and read his/her cues on whether s/he wants to stretch the question to a 30 min answer. Best approach would be: we can do this with several degrees of precision. At an high level this would be my basic structure to estimate approximate size, if we want to further refine then we can dive deeper into these segments/drivers, etc.

hope it helps,


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Andy on Feb 07, 2018

Got it. I was originally thinking that I may have to segment the case even more detailed than the normal ones. But yes, I should just follow the interviewer and go with the flow! :)

replied on Feb 07, 2018

Hey Andy,

I would support Mattia's point below.

If I was you I wouldn't pay much attention to the supposed "30min duration" itself, but rather focus your efforts and energies in guaranteeing that you can practice to answer to the interviewer's question(s) in a structured, clear and complete/comprehensive way. As far as you do it, you will be fine, no need to worry about the timings - the interviewer will push for other questions or points if he feels the need.



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Andy on Feb 07, 2018

I see! Thanks Bruno. My friend who took a 45min market sizing case at Bain also told me something similar: the interviewer will give hints if it's not a normal market sizing case, and going with the flow would make it no much different than a normal case.

updated an answer on Feb 07, 2018
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School


I would probably disagree with most of the comments above and say that 30 min long market sizing cases are not that rare.

I personally and my candidates had a couple of case at BCG and Bain that long. For example, once I had to calculate a Tire Market and we went through:

  1. Calculating the number of existing and new cars
  2. Calculating the replacement rates for Summer and Winter Tires
  3. Calculating the B2C tire market assuming that the new cars already have tires (sold via B2B channel). E.g. if the avg. lifetime of a car is 10 years, replacement rate is 1/2 and the replacement rate per car is 4/10, since the first 2 years are covered by the tires from the b2b market
  4. Calculating b2b market (new cars + commercial vehicles). Thus calculating the commercial vehicles market size.
  5. Talking about other use cases like people visiting the city and emergency replacement. Discussing the variability in geographical coverage and different needs for winter tires.

As you may see that case can easily take 30 min. I would not take the words of the HR too serious, but you should be ready for such cases as well.




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Anonymous B on Jan 14, 2020

Hi Vlad, thanks for the sharing. Did the interviewer provide you some data or information upfront or in the process? Also, during the case, if the method / segmentation is different from interviewer, would he correct you or give you hint?

Anonymous on Jan 14, 2020

Also, is it important to ask how much time you have to solve the case?

Mattia replied on Feb 07, 2018
Looking for partners to practice cases. Currently preparing for interviews in Mck, BCG, Bain and Mastercard Advisors

Hi Andy,

honestly I do not think you should be focused on the lenght of the case inverviews. If the interviewer wants to put in front of you a 30 min- market size he will and this will be automatic. Personally I do not think you will be in the situation to have to stretch it, simply the interviewer will ask for more details if they are necessary. Just stay focus on the right approach, trying to segment the product whose market you will have to estimate when this is possible and reasonable.

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Andy on Feb 07, 2018

Got it. I'll keep myself mentally prepared when he keeps asking for details

Anonymous A replied on Feb 07, 2018

Hi Andy,

I had a market sizing question just yesterday, lasted more than 30 mins: Accenture round 1, had to estimate the market size of smart homes in the UAE.

I had a straightforward logical standard approach, validated by the interviewer.

As I tried to fit numbers to the different buckets, I was guided by the interviewer and asked to provide more detail where he saw fit.

He eventually led me to doing a market sizing within a market sizing! He did not want me to estimate the average household occupancy, he wanted me to estimate the number of housing units in the UAE and then divide the population by the number of units to get the average number of people per unit. To make it tougher, I had to segment everything by expats and locals.

The trick here was to remain calm.

So my tips to you are:

  • remain calm, do not let the element of surprise take over,
  • do not stress out (when you stress blood goes to your limbs instead of your brain, very unproductive),
  • take a minute to think and back up your numbers with logical arguments,
  • do not just blurt out the first thing that comes to mind,
  • label your data and get the maths right,
  • sense check your answers.

Best of luck!

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Andy on Feb 07, 2018

haha that's very useful! my coming interview is with ParthenonEY. Yes I'll keep calm and ready for whatever the interviewer planned for me!

Francesco gave the best answer


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