That's five times the 15m annual visitors today. (not tourists, visitors... for comparison, about 7m people visit the Eiffel tower each year, so it's more like

That's five times the 15m annual visitors today. (not tourists, visitors... for comparison, about 7m people visit the Eiffel tower each year, so it's more like 10x tourists, but let's assume 5x) On the contrary, I don't think that's feasible at all. The average tourist stays about a week. That means you've got about 1.4m tourists in the city on average, on a population of 2.2m. In other words, tourists as a group are about 60% the size of the local population. Then consider that tourism follows a sort of bell curve with months along the x axis. A month in July has about 2x the monthly average, so at peak holiday season you're looking at there being more tourists than locals in the city. That's an insane proposition. Similarly, tourism isn't spread out, but rather concentrated, the city centres become uninhabitable. Then consider the dynamics on the local economy. If you've got 3 billion (or 75 million) people's worldwide income bidding for some real estate, some food etc, against 2 million locals, prices will go through the roof. Local population will atrophy and the city turns into an open-air theme park. And that's assuming a single visit. I've been to Paris half a dozen times and it's not even a place I ever deliberately thought about wanting or needing to visit. And I'm sure I'll be there another 10 times in my lifetime. None of this is feasible if you ask me, outside of the extremely limited scope of stating it's strictly logistically not impossible to accommodate these numbers. The sociopolitical and cultural dynamics will break.