But, I think in Rio there is also an argument to be made of how many of those "estimated" visitors are actually simply displacing people who would otherwise have travelled to Rio. To your point, if Rio is in fact no set-up to accommodate as many people as London, then a lot of the effect of the games will simply be substituting regular travelers with Olympics watchers.

Either way -- the only point I guess I was really trying to make was that the variable of interest is the delta in the actual visitors to Rio -- you want an economist making this argument, not a health expert