McKinsey Case Interview: Market Sizing Walkthrough

Watch Lisa Bright, ex-McKinsey consultant, work through a McKinsey market sizing case.

You'll see how she structures the case, talks the interviewer through her process, and comes to a final recommendation.

Even better, you'll learn from the detailed feedback Jenny Rae has for Lisa at the end of the case. Enjoy this market sizing case walkthrough!

What you'll see in this video:

◈ Ex-McKinsey consultant doing a live market sizing case
◈ Market sizing case structure
◈ Mental math
◈ Detailed feedback at the end of the case

*RESOURCES:*

*VIDEO CHAPTERS:*

[01:19] Start of the case
[03:50] Case structure
[06:03] Mental math
[18:12] Final answer
[20:52] Feedback

[MrMcfire]

Really like the fact that this was authentic; It shows that even the most experienced of us are still not perfect. This tells us that interviewers simply do not expect a perfect outcome but in fact a sound structure with 'common sesnse' and a structured approach

[kevingartner]

Very authentic interview, unlike many "perfect" cases in other videos which seem totally staged. Especially appreciated the honest feedback at the end. Thank you for the effort!

[nileshjha]

The calculation at 16th minute is fun, she is adding and subtracting 10% from each side and then wondering what the answer should be...36

[anishmondalzen]

Hats off to Jenny. As the interviewer, keeping a track of the calculations is no mean feat. She did it so easily. Also, Even though Lisa stumbled, her presence and composure were very good.

[sayantanibandyopadhyay]

If each diaper costs 2 cents, shouldn't she multiple 1400 diapers with 0.2 cents instead of dividing it?

[dnote-na]

Chinese currency is not Yen but Yuan. Yen is Japanese currency. It doesn't sound like a big difference in English but to people who are familiar, they are completely two things.

[meoconrabbit]

Super helpful. Thanks Lisa and Jenny for walking us through this exercise.

[SamarthPran]

When I heard disposable diapers, I thought that maybe there could be 2 kinds of people who could use it....first and obviously the babies but second, maybe adult diaper market could also be considered. Now I know that it would not be a huge market or maybe even a significant market in comparison to the diapers market for babies, but I suppose to show MECE approach, one could have considered it and then later with the mathwork show that the adult diaper market is insignificant to the baby one. Just a thought.

Otherwise I thought the the structure was pretty apt

[peggyzhang]

"Market Size" and "Market Value" are different. I thought this was a market size question so I ended up estimating how many disposable diapers are there in the Chinese market per year but as interviewees, we should clarify this question at the beginning.

[michaelscott]

Just to add. You could have added adults as well (Age group : 60+ years)

[its_georgie]

Loved this interview, thank you both for doing it. Very easy to follow along to and gave me a clear understanding of what's expected in a market sizing case. Loved also that it wasn't "perfect", came across as very authentic!

[rishimetawala]

5/80 is true if distribution is uniform, not normal. However, really well done case and get's the idea through.

[geronimomolina]

Great technique. The only thing that was weird to me was the population estimation. A population pyramid is far from a normal distribution in terms of age and specially in a growing country such as China.

[shritisingh]

She handled it so well. This was tough!!

[flointhefflow]

The content is really helpful. However, Yen is Japenese currency, Chinese currency is Yuan or just RMB. Big difference.

[huanransun]

Logic is reasonable but math errors are keep distracting me: Spending on disposable diapers per week= 280/50 = $5.6 which can be rounded to $6 per week instead $4. Also the # of children within the age range (0-5): 1.2BN * 5/80 = 75M.

[mohamedoubari]

I was expecting a better performance from a Mckinsey consultant. She did many math errors and wasn't able to do a sanity check for the final number. But great work thank you.

[aufa]

Good one! However, how about the adult disposable diaper market? Shouldn't she have clarified about it earlier? (Or did I missing the clarification of baby-only market?)

[bettyaugust]

Thank you so much for the video! I guess one factor that has to be taken into consideration is that the penetration rate would be very different between urban and rural areas - for urban areas, probably 95% of babies would use diapers; but for rural areas, which accounts for a significant proportion of the overall population, the % could drop to 20% or even 10% (assumptions made based on their income level and access to disposable diapers).

[arindambaruah]

Super impressed by how closely were the calculations tracked. For the preference of the disposable diapers vs reusable diapers, I would've probably asked for some research related numbers. When I did this case myself, I used a 50-50 split which luckily came out to be 35 million. However, the interviewee's numbers based on the rural vs urban population was probably a better way to work out this number.