The best way to learn is by doing :) Post your approach here and we can provide feedback!
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 relevant industry? Then break it down that way.
General Tips for Market Sizing
- Just like in a case, make sure you understand the question - what are you really being asked to calculate
- Decide whether a top-down or bottom-up approach is best
- Figure out what you know you know, and what you know you don't know, but could estimate
- This helps you determine how to split out buckets
- 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