I was asked this question by a Principal at an MBB and I'm not sure I got the right methodology. Here's an idea of what I did:
1) Estimate the number of hotel guests:
- 3 segments (local tourists, foreign tourists, business travellers).
- For locals, I assumed that X number of those aged 18-70 ever go on holidays, of which Y number of them decided to visit France, and Z of them didn't have friends/family/secondary residence.
- For tourists, I told him from what I read recently, there were ~90M tourists visiting last year (really not sure about bringing a personal knowledge in that case..)
- For the business travellers, I just assumed they represented a fraction of foreign tourists - 5%. Why 5%?
2) Multiply by their respective average hotel stay: assumption was that foreign tourists stayed longer, then business travellers and then locals.
Needless to say he was neither please by my methodology nor my answer. If anyone can help me figure out/understand how I could have better answered this question, it would be appreciated.