1) The effects of tourism on housing prices: applying a difference-indifferences methodology to the Portuguese market. https://www.emerald.com/insight/content/doi/10.1108/IJHMA-04...
> Following the liberalization [allowing more AirBNBs], for each one percentage point increase in the share of STR as a percentage of the housing stock, housing prices increased 27.4% and 16.1% in the Lisbon and Porto MSA municipalities most exposed to STR, respectively. These results represent a much higher impact than that estimated in previous studies (Franco and Santos, 2021)
2) The impact of Airbnb on residential property values and rents: Evidence from Portugal https://www.sciencedirect.com/science/article/abs/pii/S01660...
> This article quantifies the impact of Airbnb’s short-term rentals on housing affordability in Portugal.
> We find that on average a 1pp increase in a municipality Airbnb share results in a 3.7% increase in house prices.