Every three months the rate of interest used to set Swiss rents is reviewed. If it goes down some renters have the right to request a decrease in rent. This time it remained at 1.50%.
The last time it dropped was 1 June 2017 when it fell to its lowest level since 2008.
The rate is based on the average Swiss mortgage rate over three months. This rate is then rounded to the nearest 0.25%. This time that rate was 1.51%, which rounds to 1.5%
In general if your rental contract links your rent to mortgage interest rates then you can demand a decrease in rent when this reference rate declines. The Swiss Association of Tenants, Romande branch, provides useful information on when and how to go about making a demand. Their website (in French) can be found at www.asloca.ch.
Current and historical reference interest rates are presented on the Office fédéral du logement (OFL) website.