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Market sizing - commercial segment often neglected?

Anonymous A


when doing a market sizing question, most solutions soley rely on households, e.g. when calculating the number of cars/light bulbs sold (

But what about the commercial segment? There are company cars and many many commercial buildings, which use light bulbs, as well. How would you approach this? Can you simplify this by saying "I believe there are an additional 10% of company cars" or "For every light bulb in the private segment, there is another one in the commercial one"?

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replied on 02/09/2018
BCG decision round interviewer with 300+ real interviews conducted and 8 years interviewing experience

Agree, in a lot of interview answers B2B segment is forgotten by the candidate and that can lead to an average performance. I agree with all suggestions below, with one specification: personal experience is ok when is referred to "real world" observations such as 1 in 10 cars I see around is a corporate car. What is definitely not ok is to refer to personal experience in a specific industry/sector to help solve the case (e.g. I worked in lighting industry and I know that commercial segment is 1/5 of consumer one)...that's not the point of the sizing question, the point of the sizing question is to see how you apply logic and perseverance to come up with a guesstimate and what tools would you use it to confirm it in a real case.

hope it helps!


Vlad replied on 02/09/2018
McKinsey / Accenture / Got all BIG3 offers / More than 300 real MBB cases / Harvard Business School


It's neglected only if you decide to neglect it=)

I recommend the following:

  1. Ask the clarifying question first: Are we looking only at the b2c segment or other segments as well. Mentioning this by itself will give you the extra points. In many interviews, the interviewer will allow you to neglect
  2. Make a B2B branch in your analysis. But start analyzing with B2C first since it's easier.
  3. There are many tricks on how to make a B2B calculation approximation depending on the industry. Here are some of them:
  • Personal experience (e.g. when I look on the street, every 10th vehicle is commercial. Thus there are (B2C / 10) commercial vehicles. Now you can calculate commercial gas stations, Tires, etc.)
  • Calculating the space. For example, if you need to calculate the commercial real estate, you can 1) calculate how many buildings you have in the city (using the estimation of what % of the land is occupied by them), 2) subtract the apartment buildings 3) multiply by the number of floors and space.
  • Calculating the number of businesses: (Working population - % working in public sector) / (SB, Medium, Enterprise split * avg number of employees in each). For each size of the business, you can calculate whatever you want, even light bulbs used.

To give you an example:

Once in the interview, I was 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, the 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.

Calculating b2b market included calculating the tires for the new cars (B2C market of the new cars * (4 tires + 1 extra)) + commercial vehicles * (avg number of tires per commercial vehicle).



Francesco replied on 02/10/2018
Ex BCG | MBB Specialist | #1 Expert for meetings done (1100+) and recommendation rate (100%)

Hi Anonymous,

I agree with the previous comments, however I would suggest not to use personal experience, neither for households nor for the commercial sector, with small samples. Eg, if you have to estimate the number of people playing tennis in the 10-20 year old segment, don’t say “In my high school class, 2 out 24 people played tennis, so I would assume 10% of young people play this sport”. If you do so, the interviewer will likely challenge you with a “What if your sample was not representative” and, given the sample is indeed small, unless you have a relevant backup answer you will lose points.


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