Accuracy of sick people calculation

New answer on Apr 21, 2021
2 Answers
Matthew asked on Apr 20, 2021

I really enjoyed this case. However, I did get the sick patient market sizing fairly incorrect. I understand that the market sizing is more about how you formulate your answer than the exact answer. However, I think some of the key assumptions, in this case, are quite far off. Particularly the cancer numbers.

A chance of developing cancer of 2% in a 75-year lifespan is exceptionally low. The real figure would be much closer to 20-25%, and this is in keeping with China's current prevalence of approximately 1.5%. I think because of this inaccuracy and the fact that the numbers of diabetes patients are calculated off of this, these are also quite far off a more realistic number.

I calculated the sick patient numbers as much higher.

I'd be interesting to know if anybody thinks differently about this? My calculation for pregnant women was fairly accurate, but my sick patient calculation was significantly different.

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Content Creator
replied on Apr 21, 2021
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut


Glad you lieked the case, indeed there are many great ones here in the library.

Furthermore, as you very well state, the important thing are not the assumptions -that you can always double check with the interviewer also-, but the way you think and structure the problem.

This said, I agree with you, 2% figure is too low -and a simple Google research would demostrate that-. I am not if your 30% is a bit high (I also hope so, for the good of mankind), hehe. The right way to approach this would be to just ask something like:

"I would assume that 20-25% is the estimated chance for a person to get cancer in a lifetyme, does the client have any information regarding that figure to double check my assumption?"

Hope it helps!



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Content Creator
replied on Apr 21, 2021
MBB | 100% personal interview success rate (8/8) and 95% candidate success rate | Personalized interview prep

Hi Matthew,

I think your question here is great - you're levelheaded about this.

Yes, the thinking/structure matter the most.

But, having reasonable assumptions matters a lot as well! Now, clearly you know a fair bit about this topic, and you are correct (around 20-50% of people get cancer in their lifetime). Be reassured that you are right here!

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Clara gave the best answer


Content Creator
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut
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