How would you approach a market sizing of the hotel industry in any given country (US or France for instance)

Hi,

I would try to make an estimation from demand side:

1. We cant split market value into two components: $ spent by citizens of given country and $ spent by people from abroad. I think that we can make a decent estimation of percentage of reservations from abroad. I guess that for US it is less than 10% and for European countries slightly more (10-20%?). Not sure about that, but certainly it is not more than 20-30%, so we are not making huge mistake.
2. Now we need to calculate how much $ do citizens of, let's say, US spend annualy. In order to calcualate that, I would split it into business travels and holidays.
3. For business travels: x% of people 18-65 y.o. do business travels y times a year. Each travel is on average z nights and one night costs u.
4. The same for holidays, but I would look at families
5. edit: I forgot to mention that for 3. and 4. we need to include % of travels within given country 

I checked numbers for US and it seems that this approach has passed sanity check. What do you think?