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Extra-long Market Sizing Question


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 02/07/2018
Former BCG decision round interviewer with 300+ real interviews in 8 years

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,


Currently non-active expert
replied on 02/07/2018

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.



Vlad replied on 02/07/2018
McKinsey / Accenture / Got all BIG3 offers / More than 300 real MBB cases / 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.




Mattia replied on 02/07/2018

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.

Anonymous A replied on 02/07/2018

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!

Francesco replied on 02/07/2018
#1 Expert for coaching sessions (1700+) | Ex BCG | 850+ reviews with 100% recommendation rate

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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