That's great in theory, but in practice has literally dozens of ways to be bypassed. Rents in Bavaria and Berlin have increased by nearly a quarter over these past 4 years.
One of the problems being that the Mietspiegel only accounts for new rentals, with steady increases in rent prices, it does not reflect the actual "average rent prices" because it's missing data for people who've been living in the same place for years and up to decades, with the same low rent.
