What measures can be used to keep rents in check?

Rents are rising in all major European cities. Politicians are trying to counteract this in order to keep housing affordable. Which regulations are promising?
Whether Paris, Berlin, Amsterdam or Dublin – the research in 16 major European cities shows: In all of Europe’s booming metropolises, affordable housing is in short supply.
In Berlin alone, the average asking rent doubled between 2008 and 2018: from 5.59 € per m² to 11.08 €, according to data from the German Federal Institute for Research on Building, Urban Affairs and Spatial Development.
Cities are trying to stop this trend with various instruments. From steady new construction to rent caps to the public purchase of houses – we have collected ten measures against rising rents and asked experts- including Barbara Steenbergen, head of EU office of the International Union of Tenants www.iut.nu , which they consider particularly effective. “