They are freeing up ~10,000 houses over the next four years with this legislation. Barcelona built ~15,000 new properties between 2011 and 2020.
The math don't math. It's a drop in the bucket. The entire impact of AirBnB + all housing built in the last decade does not offset the last half decade of population growth.
Housing must be built more quickly than your population is growing to keep prices down, or you must concede that you live in a nice area where people wealthier than you wish to be and that those people are going to gentrify the area and displace locals. It's an unpleasant reality of the world.
EDIT: some good feedback in the responses. thanks! I'm being a bit dramatic by saying it's just a drop in the bucket, this action frees up more housing than was built over the same timespan, and it's possible to have effects on pricing greater than what would be inferred by the raw numbers because economics is tricky. cheers.
Since this is HN, I was expecting a little more rigor in proving the math not mathing: how many people can be housed in 15 000[1] + 10 000 houses? How small is the drop and how big is the bucket?
From sibling comment, average density is 2.51 people per home * 25k houses which works out to 62 750 housed people out of the 100 000 population growth. If my math is correct, that is significantly more than a drop in the bucket, considering the Airbnb component is 40% of that number, or just over 25k people - which is a big drop indeed for a 100k bucket
[1] Edit: I later realized your comment has numbers from multiple time windows. Substitute "15 000" with whatever number of houses were built/added in the past 4 years.