It's true that Airbnb is only part of the problem. A larger problem is that there is a lot of illegal temporary renting, in fact many people I know have never seen a rental contract. Officially, there needs to be a sign on the house for "alojamento local" but few places have it. I can't blame the apartment owners, if you have another place to stay just renting out one apartment is enough to make a living.

But the problem is even deeper, I recently spoke to a friend on the phone who considers to move to Portugal. He told me that if he rents out his apartment in L.A., he should get about 10,000 USD/mo for it. For that money he could literally rent a whole house in Portugal. How could Portuguese with an average salary below 1,000 USD compete with that on the housing market?