Berlin Mietendeckel (2020–21) — A City-Level Rent Freeze, Struck Down, With Two Quasi-Causal Evaluations

In 2020 the Land of Berlin enacted the Mietendeckel (MietenWoG Bln): a rent freeze and caps for flats first ready for occupancy before 2014, the first law of its kind in Germany.
On 15 April 2021 the Federal Constitutional Court (2 BvF 1/20) declared the law void because rent-level rules for private housing fall under federal law (BGB §§556–561); the Court did not rule on proportionality.
A peer-reviewed study (Hahn, Kholodilin, Waltl & Fongoni, Management Science 2024) finds advertised rents fell significantly on enactment, a large rent gap opened at the city border, rents in unregulated neighbouring municipalities rose, listings dropped significantly (partly permanently), and concludes negative consequences for renters appear to outweigh positive ones.
The ifo Institute (press release 12 April 2022, using immowelt.de listings and comparing Berlin with German cities of 500,000+) reports rental supply fell by up to 60%, regulated rents rose on average 11 percentage points less per quarter than in other big cities, and unregulated rents rose about 5 points more. Data are advertised offers, not signed contracts.
Lesson for cities: a local rent freeze lowered prices for sitting tenants but reduced access for newcomers, and legal competence is a threshold question.

Read the full analysis: https://www.ifo.de/en/node/69033