Hi there,

You'll really get the best out of this exercise if you try it yourself. Why don't you post what you're thinking and we can help?

Hint: Do you think this makes more sense top-down or bottom up?

General Tips

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 a similar industry? Then break it down that way.

It's very simple: Do the approach the is the easiest for you given the question.

Are they asking you to estimate something where you don't even know where to begin from the top (maybe you have 0 clue as to the market size of the industry, the GDP of that country, etc. etc.)? Then do bottom-up!

Alternatively, does it seem impossible to do a realistic from-the-ground-up estimation of something (perhaps it requires just far too many steps and assumptions)? Then do top-down!

Fundamentally, you need to take the approach that just makes the most sense in that circumstance. Quickly think about the key assumptions / numbers required and whether you 1) Know them or 2) Can reasonably estimate them. If you can, go ahead!

An Example

Here is a good Q&A great market sizing question asking to estimate # of electric charging stations in a city in 10 years:

https://www.preplounge.com/en/consulting-forum/how-would-you-solve-this-market-sizing-question-from-roland-berger-7631

This one could be answered top-down (as I did) by estimating population of the city, # of drivers/ cars, etc. etc.

OR, it could be answered bottom-up by estimating # of stations you see per block (or # of gas/petrol tanks), % increase this might be over time (or # of EV stations that would be needed per gas tank given EV stations take 10 times as long), and # of blocks you'd estimate the city to have.

Here's another market sizing (with answers + explanations) to get you started:

https://www.preplounge.com/en/management-consulting-cases/brain-teaser/intermediate/taxis-in-manhattan-market-sizing-229