Yes, I was referring to the supply of housing for tourists and visitors, since that's the context the previous poster was referring to.

Regarding total supply of housing for residents + tourists, AirBNB does help here as well. There are a number of people who have extra space in their apartments that they would like to rent out temporarily, without any long term commitments or friction. If AirBNB didn't exist, these people would simply not rent their apartments at all, and that extra space would sit there unused. Thanks for AirBNB and similar services, this extra space is now better utilized to grow the overall supply.

Obviously I don't have any aggregate data on how many people use AirBNB as a substitute for renting, vs letting it sit empty. But anecdotally, I personally know multiple people who use AirBNB but would never take on a sublet/long-term tenant.