Just a small part of Swiss pension funds’ liquidity is affected by negative interest rates, Swiss National Bank Vice Chairman Fritz Zurbruegg told a conference on Thursday, defending the central bank’s policy of negative rates and currency intervention to hold down the strong Swiss franc.

“The idea of negative rates is to make franc investments less attractive. It only works when it applies to all investments. It is important that everyone is under this system,” he said. “The goal to make the Swiss franc less attractive, not just for foreign investors but also domestic investors and institutional customers.”