In China alone, spending on international travel and tourism was an astonishing $215 billion in 2015 - that’s up more than 50% from 2014. It’s easy to blame much of this phenomenon on Airbnb. After all, very few people travel far without knowing that they’re going to have somewhere to stay. But really, the supply-side story is just the other side of the coin, and the demand-side story is ultimately much, much bigger. Indeed, it’s a trend that goes back centuries.