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Guesstimate - How many polar bears are there in the world?

guess-estimates Guesstimate market size
New answer on Feb 11, 2022
4 Answers
1.1 k Views
Dennis asked on Feb 09, 2022

How would you solve this?

Maybe segment in bears living on the north pole and bears living in zoos. But then again, how can it be further segmented to come up with numbers?


Any other approach?


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replied on Feb 09, 2022
Empathic coach, former McKinsey Engagement Manager |Secure offers from top consulting firms

There are many ways to solve this problem, I give one here but it really depends on where the interviewer is going with this case, one way is 

1) Restate the case and ask a few pointed questions to give you more data and understand what's available, for example countries in which polar bears live (they do not just live on the pole) and when would they not want to live somewhere, what are factors that they need to live, (for example maybe they stay out of populated areas), what is the size of a territory, maybe they need a certain type of food to survive, are they an endangered species, what are growth rates of the population.

2) Structure your approach

One approach could be

Basic parts:

- Countries polar bears live in


- Size of these countries 

- times share of these areas that are favorable to polar bear living


- share of favorable area that is typically inhabited by polar bears 

translate this to units, then multiply by

- number of polar bears per favorable area unit (for example look at territory size of a polar bear (e.g., do they live singly in a territory or together etc))


- interviewer may change structure or you may not get this information and instead you must factor in points such as life span, birth rates, etc.

3) What the case might involve into:

I once came across a similar case with wolves, the point there was to understand how much the population changed over time, you had to look at a) base population, b) added population (mating and then birth)  c) subtracted population (disease, hunting, death) and had to look at how the living area affected this based on whether they could find mates or whether there as a risk of disease in a particular area.

I have listed a simple approach here, as said you may also find other ways to do this. If it is of help to you, I currently still offer free coachings, feel free to book one.

Best regards,


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replied on Feb 11, 2022
Bain | Roland Berger | EY-Parthenon | Mentoring Approach | 30% off first 10 sessions in May| Market Sizing | DARDEN MBA

Let's use a top down approach. We can start with total bears population, segment according to the type of bears, and then…

Just kidding here. This is a very specific question and providing you with an answer won't help you with similar type of problems. It's best if you give it a try yourself.

In any case, here's my answer. We need to consider polar bear populated area * polar bear density per area.

You'll need to have some basic geography numbers in your head to do this. For example, I know that Portuguese population density is 100 people per km2 (and there are 10million people in the country). So that's 10m/100=100.000 km2 in the country. 

So let's assume the relevant polar bear populated area is the equivalent to 20x Portugal (that should be close to Greenland), and that there's a polar bear per each 50kms. I know that a lion needs several kms. So a predator in a cold area will need much much more.

So that means the area is 100.000 * 20 = 2m km2
And the population density is 1/50. 

So polar bear population is 2,000,000 / 50 = 40.000 bears.

Does this sound reasonable? We hear that it is an endangered species, so I feel comfortable with this number (for example 4 million would not make sense for an endangered species).

Note: there are 20-30,000 polar bears in the world.

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updated an answer on Feb 09, 2022
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Hi Dennis,

Why don't you try to solve this yourself and then we can review!

Remember that there's rarely a "best" answer with market sizing. What's important is that you break down the problem the way it makes sense to you. Importantly, break it down so that the assumptions you make are the ones you're most comfortable in.

For example, do you know all the major brands? Great go with that. Do you understand all the segments of that country's population (either age or wealth or job breakdown)? Go with that. Do you know the total market size of the tourism (or hotel) industry? Then break it down that way.

Some tips:

  1. Just like in a case, make sure you understand the question - what are you really being asked to calculate
  2. Decide whether a top-down or bottom-up approach is best
  3. Figure out what you know you know, and what you know you don't know, but could estimate
    1. This helps you determine how to split out buckets
  4. Stay flexible - you can start with a "high-level" market sizing, but gauge your interviewers reaction....if it looks like they want you to do more...then go along level deeper in terms of your splits

Here's some practice:


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Anonymous A replied on Feb 09, 2022

They are being wiped out by climate change and human activity. How to calculate this & how relevant is this question in interview anyway? I will be keen to understand the calculations too.

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Dennis on Feb 09, 2022

Question was asked in OW interview

Charlotte gave the best answer


Empathic coach, former McKinsey Engagement Manager |Secure offers from top consulting firms
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